Awesome! Sounds great, yeah if you do a nice looking battery holder where the engine was I think it could be really sharp. Moby chrome in general is crap so if you really want it to look nice, you'll probably need to source replacement, but keep us posted on how electrolysis goes.
As for stretching the swingarm I think you'll be fine. It's got no value for anyone as a spare so don't sweat that. I have a large 3/4" bolt and coupling nut that I use with wood blocks, like a mini screw jack. You'll be surprised at how flimsy and easy to bend they are in that direction.
Otherwise, just cut new metal plates and weld them on. If you bolt the wheel into place and center it before you weld, it will be fine. Obviously you want the wheel straight but it's not that precise to be honest.