I see two obvious ideas here:
One: for each energy you decide NOT to spend before each game, you get a percentage increase in your trophies that game, and a percentage decrease to trophies lost. (Though I can see problems with this being exploited by boosters).
-Example: 5 energy not spent -> 50% increase in trophies gained.
-This rewards risk, giving up powerful starting resources in order to gain greater prestige.
Two: a new ‘perk’ called economy. For each energy you put into it, the speed at which you you generate random power-ups throughout the game increases.
So for instance:
1 energy in economy generates 1 crate every 2 minutes (base case)
2 energy speeds up the generation to 1min 35 seconds
3 energy speeds up generation a little less at 1min 25 seconds
Etc down to 10 energy generating 1 crate every 40 sec
There’s so much you can do with choosing not to use all your energy on perks. There’s were just random ideas with random numbers, but I’m sure this community can come up with more.