If the engine can display it like it displays selection rings that shouldn't be a problem visually.
Just tested this with the Flak HT: the game hides range rings if you select multiple units. As for infantry, how much variation is there in max range? Ideal range varies wildly but I've never seen an infantry squad be unable to fire on another infantry squad attacking it before.
Selection rings are right next to the model tho, i think that does make a difference. I dont know if most weapons share the same range, or if its very individual.
In any case, keep the low rate and limited scope of patches for this game in mind, further implementations of features such as this seem very unlikely.