I feel like the V2100 wouldn't be much cheaper to outfit than the EM3EV frame. A lot of guys put a different swingarm on them and the fork is just a Walmart level fork. It looks like the triangle wouldn't fit my battery because of the rear shock. It's also pretty tall for me. Would be a pretty good bike to start with, though, plenty of upgradability while being cheap to start with.
I got
this backpack for the battery. Main pocket seems like it was made for my battery and the other pockets are quite spacious. Ebike felt great to ride with the battery in this bag. I still have to work on getting the straps adjusted just right, but it feels much more secured to me than my other backpack. I'm going to cover the controller in the triangle with coroplast tomorrow to make it a little more stealthy/less bomb-looking, then I'll post some pics of the bike and bag.