My assumption would be more Aeon stuff and more side story/walkaround content. Especially to make repeat playthroughs to get different main story paths a bit more varied.
I do agree that the route locks are a bit annoying, but I also get why - The major routes are, well, the major routes. They're the ones more about Chelsea's life long-term, not random flings. However, them being major means there's likely to be crossover between events, and the number of events and interactions goes up exponentially with how many of those paths there are. The game is already taking a while to get done, so cauterising the paths so that you aren't doing... 16(?) potential variations on a scene based on main routes alone, is probably wise. Might be more feasible if the game was structured differently, although I think a lot of the main paths would be plain incompatible or have entirely different stories if running concurrently.