The chances of this happening are a rounding error. Red Bull need a #2 who is fast enough to pick up wins when Max can't and take points off his rivals.
They need a Bottas, not an Alonso.
As an armchair team principal, I'd take even Bottas over Alonso. And Ricciardo over either.
Unless Alonso commits to the mother of all 2nd driver contact with an iron-clad non-disparagement clause.
So won't happen.
As a fan though, I'll pray to whatever deity to let it happen, what delicious drama we'd have on our hands.