This is a great summary of a complex topic, but I wouldn't put safety or experimentation as the primary driver. As you suggested, MOSAIC is likely a way to migrate people off experimentals to discontinue that little idealistic free-for-all.

The vast, vast majority of pilots are aging out. The vast majority of builders are retired. 30-50 years of experimentation has exhausted most people, who now just buy the tried-and-true design and kit from Van's. Many people wasted their lives on projects that never fly, and most deaths and injuries come in the first few flights.

Old airplanes are cheap and mostly just as functional as new planes, making it really, really hard to sell a lot of new planes. And there aren't enough numbers to justify selling avionics or engines, etc. unless you already have certificated products and want to reach the Van's customers. So not really enough market, notwithstanding the breathtaking improvements in electronics and composites.

The major costs in flying are gas, hangar, insurance, and maintenance, which is not going to change with these rules, particularly since they don't resolve the uncertainty around leaded aviation fuel. Those costs prohibit flying except for the wealthy or the super-motivated upper-middle class.

LSA's are safer because they're new and mostly Van's, and don't really invite scud-running or stupid fuel decisions. The push to MOSAIC is mostly the FAA trying to stay relevant, and eventually to kill experimental aviation.

I could see a new business model, where a company like Van's offers an all-in-one packages of long-term lease + insurance + maintenance, particularly to buyer's groups. Sharing a plane gets it flown more, and group members can come and go. The company gets the benefit of its own engineering effort in low maintenance and insurance costs. Rotax, Continental, or some new electric consortium et al could make deals with such companies guaranteeing enough new engines to justify new product lines. If there's a behind-the-scenes driver for MOSAIC, it might be some deal-making contingent on more sympathetic and predictable FAA regulation.

Private and experimental aviation is not stymied by product fit as much as market fit and transaction cost risks. If MOSAIC helps with that, it could be a game-changer.