Well Leo, the thing is, if you want to be trusted with other people's funds, you'll have to step up and do stuff properly. Simply not wanting a big cut for yourself is fine and all, but it doesn't make a potential user's choice to use your service any less insane. It's an exchange, after all. If you'd rather just donate your time and effort to bitcoin stuff in general, perhaps take a look at this old post. There are plenty of things you can do that won't put this sort of weight on your shoulders.
Because make no mistake, it is a weight, and you need to be able to bear it. Roughing it to see if you can maybe eke by helps no one.