They would be stupid to overlook Bottas if they genuinely ostracise Perez (which they should but the media around this is getting daft now). Bottas has proven he can play the no2 role in a top team, he's a safe pair of hands in all conditions and he's not a prima donna that will upset the status quo. He did suffer under the pressure of trying to beat Lewis but with a clear no2 contract that could be different. I think for a 1 or 2 year contract he makes the most sense and will likely retire not long after anyway. Otherwise they'll be in contract hell to try and extract Sainz forcing Williams to keep Colapinto, but Sainz will want to be fighting Max and I think it's clear they don't want that.
If they did take someone outside then Yuki is going to be spitting feathers. He won't want to be the no2 and I think that's the problem. If he was fast enough he and Max would clash. I'd say he's done what he can to prove himself this year above all the other main contenders but he's a bit too feisty.