Also, scheduling is independent of deterministic execution unless you are doing inherently non-deterministic things like multithreaded shared memory accesses which you can not simulate faithfully anyways. The only thing that matters in a deterministic execution model is runs of deterministic execution interrupted with non-deterministic events injected at precise points in the execution trace.
When serializing onto a single thread you already need to define some sort of correspondence between "simulated scheduler state" to number of instructions to execute as you are already giving up on the actual scheduler (unless you do not care about correspondence to the actual schedule configuration). You just do that, but you get to execute with all of your cores until you reach the injection point (which is how replay systems can work already). Now you can execute in parallel (multiprocessing only though, no multithreading) and use blocking I/O.
If you're not looking for that then you can build your software/system to have known sync-points where you can allow a given process to stop/wait and allow other processing to occur. This can then be in-process/out of process/remote.
As you say, this ends up being a scheduler with which you have to employ knowledge about the execution/communication channels in order to coordinate correctly.