Would this sort of "steampunk" look be acceptable, or is it too realistic?
Seems okay to me, if somewhat on the fringe of being acceptable. I'll let the hardcore milsim-haters weigh in.
Same. The bright blue and bright orange are very distinct and distance the toy from looking like a real gun IMO. Although the brushed metal color does make it look firearm-ish, when you're holding it the primary colors that show are the orange and the blue. Just don't holster it.
To answer 3, 4, 5, and 7; 3. Better to have and not need than to need and not have 4. It's actually fairly simple. Just make sure you have the correct charger with correct terminals, read the directions on where to plug in and how long to leave and you'll be fine. 5. I'm not familiar with the JST plugs, but AFAIK you do not need to plug the balance plug into anything but the charger. If you have a local hobby shop, ask them because they'll know what you need and will give you the parts there. 7. If it has two metal prongs to plug into a plastic shield (most likely) then it's pretty easy. Assuming you know how to solder, just solder one prong per wire, then put the negative wire/prong into the negative side of the shield, and then put the positive wire/prong into the positive side of the shield.
Motors from vehicle power window regulators may be what you are after. They are usually worm drive assemblies, and built for high torque. If you want to pay shipping, I'm sure I could scrounge up a couple from the scrap pile here at the shop I work at.
I second this notion. Window motors are very strong, in robotics we used two of them to pull over 100 lbs of spring force back.