I think these are all good points. If playing separately had been a criteria, we probably would have never started, but that is just us.
As we acquired a little more emotional experience with this, we had some events in which we realized playing separately might come up, and had some long discussions about rules for that: what needed to be discussed first, what should not happen after, and what we needed to discuss after. Being in the dark with each other is a non-starter. If we weren't fully excited to talk about it, we shouldn't be doing it.
Strong and open communication is vital no matter how you structure it, and understanding why she'd feel distracted with you present is perhaps a good starting point: not because it's a bad idea, but perhaps if there's some mistrust or doubt you need to talk through before you do whatever it is you're going to do.
In practice, we've only applied our "solo hard play" rules once each, her for an FMF and me for an attached woman who wanted a bull. We followed our rules rigidly and, frankly, she went above and beyond to communicate before, during, and after. Jittery, yes, but it made for a lot of trust and good memories.