In-house the market has changed, the conditions have changed, the price has changed the only way around this problem is to design and engineer around it in-house. The design and engineering capability isn’t the problem, money isn’t the problem. It’s whether or not the new CEO/Apple have the will to do what’s necessary. That’s pretty much the bottom line… they have done it before (Intel/Qualcomm), and they now have to do it again.
In-house, Apple has no fab. They have labs, but manufacturing memory would make them critically reliant on an expensive fab partner, probably driving them back to be an Intel customer again.
Design, engineering capability and money are all a problem here, and the onus falls on you to prove otherwise.
I think they just have to fund a facility specifically to meet their RAM needs. It will take time but it's only a production issue.