I'm riding a Trek 7100 hybrid - pretty heavy
How heavy is heavy?
I really don't see why you shouldn't be able to install a kit on your existing Trek - that is if you like to tinker and are good at it.
Personally, I'm more of a turn-key guy so I bought a fully assembled ebike. But that's just a personal preference.
To be honest, I also think that there are some better value propositions out there beyond Trek and Bionx.