That’s the exact opposite of the work schedule I’d want if we were doing seasonal variations in working hours.

Except you're not going to be more productive working those additional hours in the summer, so as unless you're willing to take the respective pay cut for working less hours, this proposal is a non-starter. Personally, I'd argue that more (smaller e.g. 15 minute) shifts would be better (and you could more closely track sunrise), and avoid the hard shift which it feels is the main complaint people have with switching timezone.