Chiwetel Ejiofor would be a contender for me.
Very suave, and a great actor.
Kit Harrington looks and sounds good to me, but aside from his relative young age for bond (although with bond being around for so long it’s not like it’s the same guy or he’d be a 100 by now!) I think there would need to be a gap between Got and Bond.
Jon snows character is heavy on the brooding the strife, the weariness, we’ve got a Bond like that at the moment, although Daniel Craig’s does have some lighter moments, his portrayal of bond has been bleaker and more real than some- like Brosnan, the bond I grew up with, his portrayal was much lighter, showing the dashing suave side more than Craig.
So for Harrington to go from brooding to more brooding is a bit samey, and what people will come to expect as his typecast.