Imo this is a good idea but waste of time for an ingame solution.
The game's api is not meant to support such projects and sending everything by mail? My mailboy is autofull at the moment because everyone is sending stuff, I get rewards etc.
So what about mails from an ingame raid planer that simply won't reach me
There are many raid calenders available outside the game and thus even browsable as you sit in the train on your way back home from work etc.
My experience with raids and registering for it:
Ppl do it properly, ingame or outside a game, if they are interested in raiding. And they want it easy and managed automatically. So I'd stay with eqdkp+ and others, like this solution here maybe:
http://www.esoui.com/forums/showthread.php?t=402