This idea is burning further into my head. I like many people are time constrained so I really don't need 600wh+ of battery. Build the bike around a smaller form factor 300wh battery thus keeping weight even lower in both weight and COG.
Looking back at what Vouilloz did with the Lapierre Overvolt GLP 2 he looked at battery options to drop weight.
https://s14761.pcdn.co/wp-content/up...1-1140x760.jpg
The look of this thing has grown on me. It comes with the lighter 500wh block mount battery rather than the heavier in downtube option, and it opens the option to run the smaller lighter 300w option.
Basically build a bike around mounting a Rockery Overtime size battery (300w) and own a second one that you can toss in your pack. The smaller 300w batteries weight about 4lbs.