They won't have answers for every hypothetical I'm afraid. I think all anyone can say is that if things have taken a turn for the worse enough that they need to cut entry even further, the event probably isn't going ahead.
Lets be honest most US stars will probably not attend events overseas due to covid so why not support our own actors within the UK.
I would love to see the following UK actors:
Bernard Hill
Ben Kingsley
Jared Harris
Richard Ayoade
Isaac Hempstead Wright
Simon Pegg
Ralph Fiennes
David Walliams
Stephen Fry
Matt Lucas
Emma Thompson
Art Parkinson I know he is Irish but would love to see him back at a con.