A diamond drill is fast already right? So it gathers materials fast? So imagine putting, say, Fortune III, you more than double your output! For the same cost! Wouldn't you say that that is unbalancing? How about enchanting a nano-blade with sharpness V. This will almost-always one-shot mobs and it never breaks, it just needs recharging. IC is balanced for MC without enchantments, so logically adding enchantments will unbalance it, right?
So maybe create an enchantment limiter that would only allow you to place Level 5 and below enchantments on any (except bronze stuff) IC^2 items. It is possible, right?