It seems to me the most preferred and realistic options are Neilson and Ellis. If that is the case, we might as well bring in Neilson as manager, but make the offer conditionally on the basis that Ellis would be staying as his assistant.

I don't think Ellis would have any problems staying on as no. 2. Neilson might see not being able to choose his own staff as a deal breaker, but then again, he might be happy to inherit Ellis' understanding of the current squad/league.

Could be quite a good partnership on paper?