My pick for Avon would be Colin Salmon, who's done a brilliant job playing him in the recent audio dramas. James Purefoy would also be superb, but his profile is now quite high and he's moved into making films, so that may be out of the question.
But I hope someone does finally extract digit and give us a new imagining of B7 one day, even if the current project has fallen through. We're starting to watch the whole cycle again from the beginning - having just finished the wonder that is Firefly for about the fifth time, damn those idiots for pulling the plug on THAT one! - and the early episodes are pretty hilarious. Wonky sets, lots of repeated footage, extreme reaction shots beyond what is actually necessary. And of course the old quarry appears in about the third episode and never really goes away.
It would take hard work to beat the tug of that fantastic theme music though. I wonder if they'd keep it, or a jazzed-up version of it, just as they did with the Dr Who theme.
Have you heard that they once planned to have Stephen Pacey (Tarrant) sing lyrics to it? I think the words exist somewhere, something like 'lets fly to Andromeda, my love' or something equally as daft. Season 4, as I recall. I'll have to search for them.