I've printed ABS without an enclosure on a Prusa i3 MK2s but it was not a particularly large or troublesome print. I've seen 'net references to kits for enclosures indicating such an idea is valid.

The MK2 is tougher to build than the MK3, but it was easy. One of our members built an MK3 about a year ago and said it went together with minimal problems. He overtightened something and broke it and Prusa replaced it free.

The mesh bed leveling is fabulous and the print quality is top notch. The public library at which this Prusa resides has had zero problems beyond wearing out the PEI coating, not realizing one should locate models differently from print to print. The replacement PEI has lasted more than two years since.

I've been a big fan of Prusa printers since seeing the library printer and would have one for myself if not for the underused collection I have.