As I think we've all seen thus far, there are no simple programming changes in the Disney universe.
(I think, eventually, it'll be a variation of the WDW system rather than a Flex system upgrade. The Flex system wasn't chaotic because it wasn't that heavily used.)
But I think you're underselling the potential complications of doing what you're describing. Doesn't mean they won't, but treating the 15% capacity weeks as something else simplifies the process. They can limit what tickets people can buy and use, and not have to deal with the headaches, for example, of refunding people's parkhopper tickets when parkhopping isn't available. (That's what WDW did).
I would bet the money in my wallet that it'll be something similar to the Touch of Disney checkout system initially - at least for the first few weeks. Pick your reservation day(s), pick your ticket, one-step checkout. That way, people will know what they're getting for their money, and there won't be the risk of people spending money for tickets they can't use in the near future. If the only available ticket is some form of CA-resident ticket, they've basically sewn it all up.
And I wouldn't look past the CA resident restrictions. The battles with the state thus far have been intense. The only way they skate past it is if they negotiate it away or if the state indicates they won't enforce it. Disney has to at least pretend to take it seriously.