Here is one way to do it. Sorta.
Just like the Bills have two stadiums. Bucs play half their games in Florida half in London. Any west coast teams would play in Tampa only East Coast teams would play in London.
East Coast to London is not significantly different than east coast to Sea.
The Bills don't have two stadiums. They played 1 game a year in Toronto for a few years and have now stopped it. Hardly having "2 stadiums" when you give up just 1 home game a year.
Jacksonville is working on getting a deal like you mentioned above though. Half their home games or 1 more than half need to be played in Jacksonville to fulfill their lease agreement. But the rest of their "home games" will be played in London. Shahid Kahn has been pushing for that for a couple years now, hasn't been able to make it work .....yet.