having tanks will hurt your fuel economy just like how having infantries hurt your man power economy. and heavy tanks would have higher fuel upkeep. a good suggestion from the past was 0-1 fu/min for light tanks/vehicles, 2-3 fu/min for medium, 6-7 fu/min for heavies, 8-10 fu/min for okw's super heavies.
this means having any vehicle would delay your next one, which means massing your tanks would take longer and even if you do, your fuel won't stockpile like crazy so you can just get an instant replacement once you lose them.
this would affect heavy tanks more and thus having more than 1 tiger/is2/isu/kt/jagd/ele would hurt your fuel econ so bad that it wouldn't be ideal.
It can also completely enforce people to play only infantry until heavy of super heavy hit the field. It is already something happening today, you know blobbs into call-ins meta.
So yes, maybe it would limit heavies or super heavies by 1 per player (not sure of that). But it would not solve the underlying issue: Why do people wait for heavy instead of going stock units.
So in fact, if you make sure people are spending a reasonable amount of fuel early and mid game to stay on the field, heavy and super heavy will be naturally limited.
So by ensuring people cannot reasonably stay on a game with only infantry spam until heavies are available, you make a natural limitation of heavies.
This plus territory popcap like in vCoh.
if relic wants to limit heavy spam, they need to redesign the fundamental of the game, limiting comeback situations from a game mechanism perspective. So make the game harder to learn, less casual friendly, the opposite of their strategy since OF.
Another option, and I assume Relic is looking into it is to specialize heavies and super heavies like they did with USI/Jag.
Why a Tiger should be a treat for infantry, why is it capable of wiping with 1 shot many different infantry squads? Same for IS2 or any other Heavy/Super Heavy. There is here again a design flaw, making ultra late units super effective vs anything at any ranges.
Those units should be really dedicated with strength a weakness, And I'm not only talking about rear armor. A Heavy tank shouldn't be a treat for infantry squads, it should be the opposite. Each of them could have, like the Jag a close blind area where they couldn't fire with their main gun (at least on infantry), only rely on their MGs if available. So you had more micro and make having 2 heavy, instead of 1 heavy + medium support units, less efficient.
I mean, there are so much ideas possible to balance it, so much to do with the design before looking into any kind of limitation...