If we have #[distributed_slice], then I think it's fine to push any framework that takes main away from you to offer a distributed slice of fn() hooks that it runs early in the life of the program. This means that you don't automatically have #[startup] with whatever framework, but it gives the framework control over when and how the startup hooks are ran. (So e.g. they can run after logging is initialized, or w/e.)
Ordering is still an interesting question to answer, but it's now answerable in userspace (e.g. the bevy scheduler) rather than needing to be solved in the compiler. (And there definitely are competing answers as to how to solve startup scheduling.)
(Side note: I really want to see a world where bevy can use distributed slices to construct the world. They've considered and rejected using linkme because of the platform limitations, but if it were built into the compiler directly, it definitely would get reconsidered.)