The most big problem with the game is that is complicate to understand what tyres to use with a specific temperature because isn't possible to know after how many laps the tyres becomes overheated and what is the time with a tyre overheated. If it where possible to simulate a race during the free tests, maybe using the used engine first to change it, it would be easier to understand what tyres to use during the race.
For example, in a hot race like Abu Dhabi the SS run 2,1-2,2 second faster than H but what will the times during the race with 40°C and the SS overheated and the rythm on very low? With a simulation of race (in the race window like the real race) would be possible to know it. Maybe could cost 100k€ or something like that.