Advanced troop

I think that new levels of troops should not monolithic, so we always advance the troops in the same way.
how about we need to make a decision when we want to upgrade a unit, for example:

The next level of Wizard will be a 3 way choice, make him stronger (more hit points) but he will lose speed and move slower or make him move faster but he will do less damage or he will do more damage but will have less hit points.

This way we can have different kinds of upgrades and we can differentiate the troops (for example, moon wizard, sun wizard, light wizard etc'). Once you decided on a path the troop will have to advance in that direction (if you want stronger he will become stronger each upgrade but he will become slower and slower with each upgrade) and if you are unhappy with your path, you can abandon that path (and lose all investment in upgrades) and return to the first time you decided on the upgrade path).

M.

i think an improvement to this idea is the ability to be able to upgrade all the abilities and be able to allow your troop to switch between them anytime you want (of course there would be a cost to change the ability)