How usable out of the box would that be? Or is it a case of bushings and head right away?
Impossible question to answer.
Both of mine have been good out of the box. The range was decent, the accuracy wasn't too bad either. One of them had a fuse issue where a 7.4 lipo would make the fuse glow red hot without blowing that was causing significant slow down. A new fuse sorted it.
The plastic bushings are only as good as the parts they have to work with. Perfect gears well shimmed and lubed they can last a long time, Gears with the odd burr, no grease, badly shimmed they will have a significantly shorter life. I would expect at least a year out of them, The gun is certainly not going to have problems in the short term because the bushings are plastic.
Personally I would do them in the first few shoots of having the gun, not because they will have significant wear in that time period, but because the spring twanging, and piston slapping would be doing my head in after a few games with it! So they would get done as a side effect of removing the piston slap. Gearbox is open for one problem you may as well spend the £ and get the bushings and shimming done at the same time. The motor can be done any time, as too can the wires/mosfet because that can all be done without opening the gearbox.
The hops are good. They don't need upgrading at all, They lift well, and don't wander provided the ring and ring seat is clean and free of grease. Building them is different to an M4 unit, the bucking is cut, and the brass ring goes in touching the bucking rather than after the C clip. The brass ring in deep is important as if you put it at the end of the hop like normal it can stop the hop moving fully out as there are 2 screws that will catch it.
The 2 screws that attach the hop to the outer need to sit in the 2 slots on the hop without touching the inner barrel so the unit can freely move on the spring. Elongating those slots if needed and stretching the hop main spring has 2 effects, better seal to the gearbox, And a tighter body pin, It's a 2 minute fix.