Based on old game Grand Prix World.
Could we have Tyre, Engine and Fuel R&D?
If we where to get R&D for suppliers and have 2 Test Tracks, one before season starts & another in the middle of the season.
We would need 3rd Test Driver too, Also (if adding crashes) the Test Driver would be useful in the event of one of the drivers having a bad crash and get seriously hurt and be out for a few races they could step in.
Supplier R&D in Grand Prix World can be done continuously after each race, this is a bit over board limiting it to just twice a season & only being able to upgrade 2 of your 3 suppliers would be more interesting as some people might use it to upgrade only 1 of their suppliers.
Tyre R&D is selecting one of the 4 compounds soft/hard/inter/wet ( we have 6 compounds) to increase it's stats not all the compounds. so maybe this might not be possible as we cant see the performance ratings of each compound we only see ratings for the tyres overall performance.
Engine R&D is boosting overall ratings.
Fuel R&D boosts overall ratings.
Maybe that is something else to look at, Tyre information screen remains hidden until you sign with a supplier, Then you can see the performance rating of each compound.