I too find that having to make a pitstop 'just because its forced by the server' seems a bit odd, although it does an interesting element to the racing. If im in a race where the server requires me to stop, I will often try and fuel the car so that i need to get a top up about 60% through, although this obviously slows me down on short 'pick-up' races.
I would definately like to see options for smaller fuel tanks, especially in the smaller cars. Its very rare im in an online race where a uf1 will need more than 5% (minimum you can set) to get you through the race! I accept this is probably not the best example, but you get the point.
My 2 cents....