As good as Antonelli is, there are a number of caveats:
- it's a gamble as to whether or not he'll be a generational level F1 driver in the future
- it's a gamble to put him straight into a mercedes
- and it's undeniable that antonelli won't be a polished and ready to compete driver. Considering he's already skipped F3, it'd probably be at least 3 seasons until he'd be up to speed and mature in my view
So IF verstappen's signature is possible it's still a no-brainer to get him even if it means making Antonelli go through the typical route of developing at another team like Williams. You stand to gain a lot
With the way things are developing in terms of RB falling bakc into the pack, RB building engines, Newey leaving, there won't even be that large of an incentive to stay there. Mercedes is a more enticing prospect with new engine regs