The mid system would be the best choice for weigh dispersal without a doubt. My recommendation would be to buy something built from the ground up as an ebike. The long story is, if you care to read, I put a rear hub system (Heinzmann) on two Fusion STs for my spouse and myself. Most comfortable touring bike ever. With the step through one didn't have to throw a leg over panniers. Great set up. One sits upright reducing strain on aging backs and joints with the bonus of good visibility for sight seeing. However, the drive unit, battery, and panniers really accentuated the tiller effect. My wife ended up crashing badly and swore off it as a touring bike. I stripped the electronics off of one and put it on a trainer, it's incredibly comfortable to watch a movie and peddle away. The other I still ride as an ebike, but I am an old under-seat steering recumbent rider; for me a little wobbliness just adds to it's charm. Since then my wife bought a Pegasus (German brand) ebike. It has a Bosch drive system and a Shimano hub. It's a typical diamond frame but it still sits you upright cutting down the pain inflicted from leaning over most diamond frame upwrongs. Simply brilliant touring bike. In spite of it's normal appearance I may buy one myself eventually. It's clean with none of the awkwardness of aftermarket - the battery is integrated into the frame for a seamless look. It is expensive, but not any worse than the build out you mention.