I think there are a couple of shark packs now. With mine, I think I could drill a hole somewhere on the mount to match a screw on the frame of the bike. There are four screws that cover an area where some kind of controller could go, but I don't think that space is used.
I don't really trust my shark pack, so I use a couple of mini-bungees, but they would not be secure by themselves.
I think there will be battery Zuma type scooters in a few years, with batteries getting bigger and cheaper. If you compare a new Yamaha to a new ebike shop bike, around $3k, the scooter is more of a transportation solution in a lot of places. The bikes I build for $1200 do a lot for the money. But I really think every extra $100, final cost, for DIY, is losing people. I'd like to see good motors like Mac in US kits for $300, basic batteries for $300.
Hope it all settles out. You can throw the pack in a back pack for a test ride.