Availability of membership requests options

Everytime I use Og for a project, I must to "alter_form" to limit the og "membership requests" options.
Someone wants only "open" and "invite" types, others the "Invite" and the "Close" one.
This a very usefull project, and I think it's the right place to add this feature.
Now, we can select the "membership requests" options that we want to leave available for each group type.
I had only some problem in validation, maybe someone can solve it.

Hope it will be added.