Choose users for invitation via grid select

Issue Summary

Hello,

I'm testing you great module and would like to ask if it is possible to implement the Grid Select technology for user selection. This would boost the UX.
I attached a mockup of how it could work. And here the explanation:
There is a dropdown list where the user can choose the user group by context (og, role, user relationship) and then the individual users (highlighted) of this group or the whole group via the "Select all users" button.
Below is a textfield where the user could optionally enter e-mail-adresses to which the invitation should be sent. Of course, the visibility of all fields (groups, e-mail field) should depend on permissions and settings as usual. I think, the dropdown list optional -> we also could provide a grid of all available users the inviter is allowed to choose.

I know this would be a lot of work but it would make this great module much more user-friendly -> the easier it is to use, the more websites will use it. :)
If you need help with grafics, layouts, theming etc., please don't hesitate to contact me.

Stefan