Which 3D printer should I make/get?

I've decided that my current 3D printer project ("The Monster") is a dead end. It's sad but true. Problems are piling up faster than I can fix them. So now I'm looking for an easy but not overly expensive way to get to actual printing. I can reuse an extruder (Wade's), some Nema-17 (probably) motors, and some opto-endstops, but probably not much more.

So what design should I go for? My priorities are

1. Simple to build (given access to a good makerspace with a lasercutter).
2. Low maintenance (both that it is designed to not break and that what breaks is easy to fix).
3. Compatible with common software/materials
4. Good print volume compared to size

Exchangeable heads would be nice, but is not required.

Note that print speed is not a priority. I'd rather have a slow machine that works than a fast one that doesn't.

My current prime candidates are

• Something like a scaled-down X400  (but not at that price!)
• Some sort of delta printer (but they're kinda high)
• An Ultimaker (but just how easy is fixing on them?)

but I'm very open to suggestions.