There are links to a few people that have inserted some extra foam into the seats. I found it easiest to get some nice seat pads from Amazon but I'm not using them now to get the benefit of the seat heaters. I'm fortunate that my commute is short enough that I get by with the seats okay. They obviously never did testing with enough body types in pre-production, or maximum weight reduction was more important to have longest range possible.
2017 Bolt EV Premier