I appreciate this might not be everyone's highest concern but I've been thinking the FIA should change the rules for reserve drivers.
We've often seen a driver not be able to compete and there be a big question mark about who will replace him even though the team has a nominated reserve driver. This isn't a new thing since covid, even when Massa had his bad accident in 2009 his replacement wasn't certain. So what I would like is there be a nominated reserve driver for each team who will replace the main drivers if needed, no questions asked.
Some of the reserve drivers have been great such as Hulkenberg or the absolutely stunning debut of Nyck de Vries, but others haven't been. Both Luca Badoer and Giancarlo Fisichella struggled when they replaced Massa, in a large part due to unfamiliarity with a very complicated car.
What I would like to see is the FIA mandate that the teams nominate a reserve driver for that season, at least one per team, but the driver(s) can only be one team's reserve driver. So one reserve driver can't cover for several teams in case there is a calamity that means more than 1 team needs a driver. That driver would travel with the team to all races and would be at the track when needed.
To ensure that the reserve driver can actually drive the car and know how all the systems work, they would need to have at least 1/2 a day in the car during the preseason tests, and several free practice sessions throughout the season. This free practice session could be fixed by the FIA so that all teams were equally disadvantaged.
If a team decided they wanted two reserves they each would have to have the preseason time and free practice sessions. If for whatever reason the reserve was replaced the new reserve would have to have a free practice session at the next race to ensure they were familiar with the car.
The overall goal would be to minimise disruptions to race weekends when a driver can't race, and to give reserve drivers some certainty of their role and some car time so they're not thrown in the deep end if they're called up.