My own wish is for an option for single file formation laps. Don't know about anyone else but 22 Formula One cars going two-by-two and clattering each other ruins a race experience in my opinion.
Oh yes, single file formation lap and a order to line up double file (if rolling starts) when close to green flag, should be already possible because yellow flags do it, it's just about the devs putting some effort on it
Guess the main problem is, dunno whether it is already fixed, that the server doesn't move into green when the grid isn't correctly lined up. If just one driver is 1 meter to far ahead it don't work. At least this was my experience with it. On the other hand would the WFG Competition have used it if it works. But that's just thoughts.
Track creator (or someone willing to create an AIW) is responsible for creating the AI tire warming effect. The setting the player uses is "formation lap" to replicate F1-style starts or "rolling start" if you're after IRL or NASCAR-style starts... "fast rolling start" ungracefully jumps you to the teleport spot for a rolling start, so I can't recommend it.