I was thinking that it would be nice to have colorless troops (grey or black) that could be ‘equipped’ to any hero of any color.
Their power would be fixed and limited (for example 4* black troops would be like 4* lvl 10 colored troops, no further leveling) so the colored fully leveled ones would still be stronger, but they can be useful in the meantime to fill the gaps.
They could even serve like ‘trainers’ for colored troops, giving some extra experience if used as feeders.
In epic troops summoning they could serve the role of legendary heroes, with a very small percentage to get one.
What do you think?