I wonder if it could be possible to add unit descriptions IG (without the need to open to menu) for those who want it just by putting your mouse on the image during the game ?
Yes. The main issue is that the way Genie handles bonus damage (using pairs of attack vs. armor) is complicated, counterintuitive and hard to convey in a simple way, unlike other games (e.g. Blizzard’s armor & attack types, or AoE3’s tags and multipliers).
I believe it is worth doing though. It belongs on the list of “obvious improvements the devs haven’t done”.