I don't know why the visibility of the deleted questions is limited to 10k+ users, but I suppose it's done to help people to find the right answers and not waste their time on bad questions.
If my supposition is correct, the visibility of the deleted questions could be extended to the users who have starred the question, because for them it's obviously useful and maybe it's useful also to the question owner too.
Probably the implementation of this might be a little messy, but it could be a nice feature. (I suppose that actually, connected to the visibility of their deleted questions, there are other features that must be limited to the 10k+ users)