I'd bet that electric window regulators probably weigh less than the OE crank type.
When I was working at a dealership, I used to replace window regulators all the time. The mechanisms themselves are mostly plastic and thin cable with a little motor. Some of the more recent ones are like a full door panel but the previous iterations were pretty simple.
There are general 'street rod' electric window kits a available. Not sure how you'd retrofit something like that into our cars though, probably more work than it's worth.
It does weigh less, I bought one for the driver's side, it's going in this winter.
2001 Dodge Dakota 408 All Motor 11.27 @ 117.83 mph 2017 NM Mopar Challenge Series Champion.