School planning to buy another 3D printer, tentative $500 budget.

This school year was the first year my high school offered a 3D printing class, which I am currently in mostly to improve, not learn from. They started with a donated DaVinci 1.0 and received a Dremel Dreambuilder mid-year.
My teacher has told me that there are plans to buy another printer. Since there will be a choice this time round, I want to make sure that they get a good, open-source printer that will teach the students more than the current printers will.
I started looking on the same site that I got my first printer: https://www.3dprintersonlinestore.com/
Cheapest printers to be found outside of eBay, but I now know that not all machines are up to par.
I decided that since the school already has two Cartesian machines with different strengths, the next printer should be a delta.
After looking at several machines that felt too small, I came across the Folger Tech Kossel model. I knew from the start, thanks to these forums, that Folger Tech was a reliable name to look for in kits, so I investigated and found that it was the largest and most feature-packed model under $500. Sure, the other machines have freebies or multiple extruders, but the Folger Tech fit the needs I already knew about, so that's my current suggestion to the school.
The only problem is that it needs and enclosure...I could build one using some hardware and the plexiglass sheets I have at home, but I feel like there is a better option to be had for $50-100.
My teacher wants to stick with PLA for fume reasons, but he agreed that a heated bed would be useful in the adhesion/removal of prints. I have yet to tell him about the benefits and needs of PETG.
He also wanted a printer that has a removable bed, like the Dreambuilder, but I have yet to find a sub-500 delta that does that.

I do intend on buying directly through Folger Tech, as well as throwing in a full graphic LCD unit.