Re: ROVER GT bike as starting point?
Micargi's are fine for a motorized build. You will probably need to replace bearings withing a year or so (headset, bottom baracket, etc), but they are OK and look cool.
Electras and Felts are great for motorizing, but not within everybody's budget.
“You're only young once, but you can be immature as long as you like" -Unknown