Will the amount of dark energy required for the upgrade change? And perhaps skeletal archers could have no penalty in melee combat, if they are meant to be complete analogs of the upgraded version with ranged attacks.
Regarding the absence of a melee penalty, it's not entirely logical, as a knife won't hit harder than an axe, but perhaps that's what's needed.
Added 2 minutes later
Interested,
Skeletal archers become a complete analog of regular skeletons, only they shoot.
ColouredText - список заклинаний и их уровень в описании существ-колдунов