CAPALDI QUITS !NO! WHO SHOULD BE THE NEW WHO? MY TOP 20!

Stephen Fry couldn't handle the pressure he walked out on a stage show a few years ago after having some kind of breakdown.

Sorry to see Capaldi go. What a waste of a fine actor, he was so good despite the material he had to work with being so poor.
I hope he gets at least one good season.
From the above list of potentials the name standing out for me is Reece Sheersmith.
Finished watching him in the second series of Inside no.9 recently, he'd be great.
Anyone see the Xmas Inside no.9 special? Amazingly good , didn't see the ending coming at all.

My opinions,

First, put Steve Coogan at the top of the list, not the bottom. ☺

For #3 and 10 - they won't cast a non-UK person in the role for sure.

Benedict Cumberbunch is pretty busy in his film career to go back to series TV.

For many on your list -- if they got rid of Capaldi because he's too old, they're never going to replace him with someone of a similar age or even older than him like #4, 6, 7, 8, 9 and 19.

All the rest look pretty good, though it seems you stacked the deck with comedians.

I'd add Idris Elba and Chiwetel Ejiofor to the list but doubtful either would give up film roles to devote a few years to a TV show.