Suggested

Fuel Limit

I think Fuel limit set by League host could be nice
something like
1 unlimited
2 40lit
3 30lit
4 25lit
5 20lit

This i think will increase the variety of strategy and the value of fuel economy.

This is a good suggestion. It just adds more options and customisation to the game.

Is it really a positive thing though? Limit it to 30 litres and you eradicate 2 stops (in 75%), limit it to 20 litres and you have to run 4 stops or even 5, unless FE was really developed, but then your car wouldn't be fast enough compared to everyone else to make it work. Also limits the ability to overcut and gain positions that way if you have a bad quali, and would mean mediums become redundant because you can't run long enough to use them.
Most likely all it would do is limit options for strategy. I appreciate you saying it should be an option rather than mandatory, but I can't see it working.

Don't stay in numbers i didn't count its just a thought. It can be a percentage of fuel according to race for example 20,30,40% of race with base lets say 50/200 on fuel economy.

Either way, you're going to be limiting strategy with how long people can go, and FE will remain the same. Developing FE will always be the 5th priority of managers, simply because it does not increase performance as much as the other 4.
There's no way to change that with game options, only if the potency of FE is increased. Limiting the amount of fuel to a certain percentage of the race would definitely stop some strategies, even 40% would eradicate the M-M overcut 1 stop in 50% races. I know you say not to use numbers you didn't count but we have to take every situation into consideration. Unfortunately it wouldn't make people develop FE more, just make everybody overcut less and use the same strategy.

I'm sure there would be some people that would like it. I mean if the devs could make it work without limiting strategy then I'm sure a decent amount of people will do it.

"Fuel Limit" Of course will be some limited options according to that but will add challenge to races for the managers that want it and other ways for strategy. If that will not work at the end i cannot say but will be an extra tool that a host can use season by season like a "Rule" in real F1. That's the thought ;)

I think if people want to use it that's fine, but i'd rather the devs spent their time working on updates that will benefit everyone, as with their small team they can bring out too many in a short space of time

Right now the only thing that will benefit everyone 100% is adding new tracks and fixing bugs.

Exactly. Introducing a new law (even if it's optional) would only create more bugs and prevent them from developing new tracks because of time spent on something like this