If the identds are similar, you could ban using that. Just an EXAMPLE (which I KNOW is a wide identd ban) would be:
sd44646
aa54546
aa45454
If the identds are all like that, you coudl try (VERY wide ban I know):
mode # +b *!???????@*
OR, here's where regex might work better (I dont know regex well enough)..... maybe like (somebody else who knows this stuff can tell you):
on join, if the identd in the address matches [letter][letter][number][number][number][number][number], ban them via identd. Just a thought