Hello! I'm writing another one permissions plugin
http://dev.bukkit.org/server-mods/rscpermissions/
and want Vault to support it after release.
Currently I'm at that stage when I can realize more comfort interface for Vault to do this work from your side easier.
Can you give me some recomendations?

sorry, I just patch links and provide API and let people know when they are missing API that makes their econ/permission not able to be used with Vault. Generally I suggest writing your own handler so you can maintain it.