There is only one unused vowel in english alphabet left, and it won't allow umlauts because d'oh.
But you could go spr0ng, spr9ng spr6ng, or actual spr*ng as licho suggested. Or just switch to consonants.
On issue of this thread: allowing non-influencing, but "grinding" types of games could boost some activity. I.e, play some missions against omg-powered bot if you are alone, get some 15 or 20 metal to faction if win, thus rewarding activity.
Players who mind your faction getting this metal can go and scare you away by turning 1x0 into 1x1 and forth.
Also might be a thought making influence gain dependant on actual balance.