So... just don't have wholesale creation of new NP's to suit various purposes. Which, oddly enough, actually means Archer's abilities [i]aren't that scary[/i], because all the horribly broken swords are impossible to copy.

Also, something that I don't know: if this isn't main-canon Ilya and instead has limited mana, is it limited at or below canon Archer's stocks? I can see a bit of a problem if we still have infinitely-powering-Herc amounts of mana, but that limited makes NP's an impractical choice.