if you are a WISP, charging customers for internet (especially in the US) you definately need to have a public IP for each customer. There are a long list of reasons why, but to answer your question, yes, it should, as you are routing traffic rather than nat-ing it.
Other things to consider mainly revolve around legalities, i.e. you are responsible for all traffic on your public IP, so if your customers are doing anything illegal (i.e. blackmarket music, movies, etc.) you can be held responsible, whereas if they have their own public then you can pass the blame to them.
secondly, if your customers waht to have webservers, gaming, etc. you should be able to provide a public ip to them so that they can manage their own port forwarding, etc.
with 30 customers, a /26 block would give you 64 public ip's, and would cover you now and with some small expansion. blocks are cheap, and if continuous easier to manage, so if you expect to expand, go ahead and get a big enough block to cover expected expansion fo a couple years
"If it ain't broke, you're not tryin"