I think your pannier predicament is trying to tell you something (hint: take the Felt!
) Have you thought about a trunk pack (sits atop the rear rack) and/or a frame pack (fits in the front triangle space)? Maybe not ideal, but if you don’t want a backpack and your e-bike doesn’t take a front rack, these may be your only options. Also, a handlebar pack, maybe in combination with one or both of the other options, would increase the carrying capacity.
Some (hopefull helpful) links below. Good luck.
Frame (front triangle) bag:
http://www.adventurecycling.org/store/index.cfm/product/606/revelate-designs-tangle-frame-bag.cfm
Handlebar bag:
http://www.adventurecycling.org/store/index.cfm/product/634_114/revelate-harness.cfm
This place has very good prices; lots more options, so have a look around there:
http://www.thetouringstore.com/ORTLIEB/Ort%20Ultimate%20Bags/ULT%205%20PAGE.htm
http://www.thetouringstore.com/ORTLIEB/Ort%20Rack%20Packs/RACK%20PACK%20PAGE.htm
http://www.thetouringstore.com/LONE%20PEAK/LP%20Rack%20Packs/RP700%20RACK%20PACK%20PAGE.htm
http://www.thetouringstore.com/LONE%20PEAK/LP%20H-bar%20Packs/H100%20H-BAR%20PACK%20PAGE.htm