The bigger the better for the pit, with a daylight drain and #10 wire going to the pit I'd put a small lighting panel in, say 60 amp rated with 8 spaces plus a 30 amp 2 pole main breaker. Then my pump controls and starter are there also along with an outlet or two for power and some lighting for when not if you need to access ot some night to work on something.
A nice large pressure tank to reduce the number of pump starts and your ready for a mobile or the house or even a couple of outside hydrants.
Also I would not go with a crawl space it may save a bit of money but not much. A full height basement with a good vapor barrier under gravel would be much nicer working in then a crawl space, wiring plumbing, duct work, any kind of maintenance were you can stand and walk. My home has a half basement and half crawl space, the "crawl" space is over 4 ft tall but it's not enough to walk around in now for me. When I was younger it was no problem to crawl or duck walk or even just bend over and crouch and move around, now I have an extremely difficult time getting or out of there and end up having to hire someone to do the simplest things in there, such as just stringing a cat 5 cable in there.