TL;DR:
- Carlos Sainz, though sources say Aston Martin, Sauber, Alpine and Williams are potential teams where he could land
- Alex Albon
- Fernando Alonso, if he ever get lured from Aston
- Daniel Ricciardo
- Esteban Ocon, whom is managed by Toto Wolff
TL;DR:
Those merc garage appearances (like he did for Ocon and De Vries) are Toto being a driver manager, not Toto being a team boss.
I see a 0.5% chance that Merc hires Schumacher as GP driver.
Probably depends on his performance driving for Alpine in WEC
Being good in WEC =/= being good in F1, as evidenced by countless drivers.