> waiting required is of the form "X can't proceed until A, B, D, and Q are done

In my experience, this is the common pattern on GPU workloads. On the CPU (where async happens), the wait pattern is usually much simpler.

Of course there would need to be a way to not await on the CPU and pass "futures" as semaphore waits to GPU.

But all of this is just wild ideas at this point.