Suggested

Rules Tires

The league I manage in elite we have a rule you just use either medium or soft for at least one lap. 
Everyone follows. Only in elite. Mixes things up!

A 2-tire rule(currently used by many leagues) lands you back in the same vicious cycle after a few races. 

I agree with Memo, whatever the rules for compounds at the end of the day there is only one optimum strategy and once discovered everyone adopts it. After the tyre rebalancing last year, in The MJL we went about three seasons in Elite where managers tried different strategies, the optimum strategy was found and now, if you want to be in with a chance of winning, you just copy last season winning strat.
IMO we need something that changes from season to season to influence the optimum strategy. The only thing that changes regularly and is not within the control of the manager is temperature. So if the devs made the tyres much more sensitive to ambient temperature the optimum strategy would change from season to season... Did I say this before?? 🤣🤣🤣
I'm like a scratched record. (For those of you old enough to understand what I mean!)

The option that gives a variety in my opinion is the weather together with some lower margins of working range of tires.
On last update we have increase that margin so more less all tires can use on every dry condition.
We have the Live weather system so we have summer / winter on real time meaning we need 6 months on real time to see other results on tires and that is if some tires cannot be used on some conditions. Adding that with current setting of tires only on full hot (top temperature - burned tires) we have noticeable change of speed.
All this its not easy to balance and needs testing time and undo things we did already according to players will (Live weather system etc.)

Out league has just started two compounds per race and adds much more unpredicatability and strategizing as most cars in the top ten are racing with a different strategy so keeps you on your toes. 
However issue is enforcement. Someone in our league finished 2nd last race because stayed on softs. No way to punish other than shame and peer pressure. 

I quite like the idea of a limited tyre allocation per season...every team given plenty to get through the season, with various compounds...it’s up to the manager how and when they use them.

That could add a whole new dimension to the game.