You might want to look at the whole Cubify system It sounds very similar to what you want to do, minus the licensing toy designs.

Them, along with Thingverse and some others. 

All inspiration for my idea.    I want to focus on building blocks and toys with the intention of growing enough interest to get actual licensed designs for printing.

Goal is to provide a REASON for people to buy a printer.    "Because it's nifty" doesn't justify $700-2500.   "Because I can download and print ________ at the push of a button" can be used to justify that expenditure.

I'll start a thread on this when I finish up here.

The first step is to acquire several machines and create a web-presence.  Second step is to approach several toy companies and see if we can't license "official" products for 3D printing at home.  I've set up on Indiegogo,  but that's not working out at all.   Too many people funding sick puppies to the tune of $25,000 and giving money to lazy college-students for ivy-leauge educations. 

Guess I'll do it the hard way when my tax return comes. 

I also intend to support a friend's business,  friend needs buttons,  rings, hooks, clasps, and other misc items for her sewing business.    This is a case where six ultra-custom buttons can add three digits to the price of a project for her.

I bought my SD2 for prototyping a line of all-digital, analog clocks (that have no moving parts! go figure) that I starting making a year ago.  One of my concepts is patent pending, and will also be the subject of a KickStarter campaign starting the first week of February.  (I'll be sure to post the info here  ;-)
Having the SD2 has inspired me to take my concept, and turn it inside-out making a second, very different concept, that uses the same exact hardware and a slightly altered Arduino sketch.    It's been an absolutely irreplaceable tool in my arsenal, and I can say that I would still be using cardboard and hole punchers, and certainly making sub-standard parts without it.

So, soon, my SD2 will be "working" (parts of something that I will sell) vs. "playing" (hobby/gift uses).

When Xmas came around, I spent some time making gifts for a bunch of family members, the BIG Alphabet blocks for the kids, vases for the ladies, golf markers for my father-in-law, and a fife (small flute) for my uncle.

I do plan on building a larger 3D printer - probably a MegaMendel-based design, or even better, with the rotary table drive that was recently posted on ThingiVerse, a printer specifically for printing cylindrical objects (the main shape of many of my prints)
And of course, I have been printing SD replacements parts, just to have in case my jigsaw goes to pieces.

I was thinking about making a UV cured resin printer, not least because 2w blue lasers are only £35 on ebay, and have plenty of UV, but also because lasers are really cool!
but then I thought more practically, realistically, with a UV resin printer all you're really doing is moving a laser about to make a kind of 2d line drawing, I can't imagine what sort of carriage would have to be built, but I'm thinking my home effort could never match the quality and resolution of the DLP projector that the blue laser I have was pulled from...

It isn't UV laser, but it is DLP.  I already purchased the projector, used, from ebay.  I found one that also has a com port which can control things like focus.  The resolution will be very nice but with the ability to control focus from software, I can increase the density in a small area for very detailed prints or increase the exposure area for larger prints while still having pretty impressive DPI.  I will probably use something like the Raspberry PI to control it (I have one PI plus several other potential controllers on their way)... it has the necessary video output for the projector, IO pins for the sensors and motor controllers and with the right software (custom) it would be possible to just have it reside on the network and send jobs to it.

There are many examples you can find around the net for resin type printers.. this looks to be the easiest to construct for the capability it provides.  Plus, the simplicity of driving the electronics, one axis plus some sensors and a movable panel to block light during movement transition.

8x8x6 SD3 has a total straight part maximum length of 12.8 inches.

I thought it was 8x8x8

I have 3 other 3d printer designs I am working on... the first is an upgrade for the RepMan that will have a metal frame made from 35 x 2 Vex right angle pieces.  The frame is already constructed.  I just need to design the motor and extruder mounting pieces, etc.  That should put it on par with the Solidoodle but with a much larger print volume. 

The other 2 printers are resin style (one is an under carriage projector based) that will have far better resolution than either the Solidoodle or RepMan rebuild.  My goal is to make the second resin style printer capable of full color printing... we will see. It's a bit far down the line.  To make it work, I will need to build new software capable of not only identifying different materials in a model, but also generating the gcode to make it print correctly on the machine (long term project).  I am already working on the software to automatically clean and fix STLs, which will be an inherent part of my eventual system.

I was thinking about making a UV cured resin printer, not least because 2w blue lasers are only £35 on ebay, and have plenty of UV, but also because lasers are really cool!
but then I thought more practically, realistically, with a UV resin printer all you're really doing is moving a laser about to make a kind of 2d line drawing, I can't imagine what sort of carriage would have to be built, but I'm thinking my home effort could never match the quality and resolution of the DLP projector that the blue laser I have was pulled from...

so all I really need is a frame, a perspex "dish" and an x stage.

I've also been thinking about a more traditional printer.
with solid frame and cover like the solidoodle. but all steppers outside the build area underneath the frame, so extruder movements working on a core x-y style system, a z system just like the solidoodle (but with the motor outside the case)
filament supplied from an extruder also outside the case by bowden cable. with no electronics (and therefore no operating temperature) to worry about I'm pretty sure I could just heat the whole build area with a heater at the base so (hopefully) completely eliminate warping. (interested to hear opinions on this basic description)

you lack ambition!!

6" x 6" build area gives an ~8.5" diagonal.
then you also have 6" tall build area. adding support is going to let you build from a corner of the cube to the other corner.

10.3" [:D <- that's what she said]

of course the 8x8x6 SD3 has a total straight part maximum length of 12.8 inches.

Just kidding,... but kinda serious also... now i just need to find a 3D scanner.

I'm also thinking I may need to upgrade to the SD3 for the bigger print bed. heehee.

I have 3 other 3d printer designs I am working on... the first is an upgrade for the RepMan that will have a metal frame made from 35 x 2 Vex right angle pieces.  The frame is already constructed.  I just need to design the motor and extruder mounting pieces, etc.  That should put it on par with the Solidoodle but with a much larger print volume. 

The other 2 printers are resin style (one is an under carriage projector based) that will have far better resolution than either the Solidoodle or RepMan rebuild.  My goal is to make the second resin style printer capable of full color printing... we will see. It's a bit far down the line.  To make it work, I will need to build new software capable of not only identifying different materials in a model, but also generating the gcode to make it print correctly on the machine (long term project).  I am already working on the software to automatically clean and fix STLs, which will be an inherent part of my eventual system.

I have some other inventions in mind as well as some home projects.  One of my home projects is an adapter to allow 4 CFL bulbs to mount in place of a balast in a fluorescent light fixture (using 2 double sockets).  It is designed and ready to print, once I get the ability to do large prints reliably (without a jam).  Its large enough that I need to print it in 2 pieces and glue them together.

All of my printers are for personal/hobby purposes... no business use at present. 

This might be more than I can manage in the short term, but one project at a time and it will all get done. On the plus side, I have plenty of time to code while waiting for prints to come out of the magic box.  ;-)