sounds like a good idea... with some initial thoughts around it...Potential???
how about outlining what this group will do...solve problems... which dont know if a messaging group is that good for...!
Conceptually messaging groups are to be formed
To engage someone for something on urgent basis...info\to do something...!
Broadcast information...nowadays Twitter is doing that...!
Run search based BOTs...pretty sure GMATClub wont venture...!
So for preparation standpoint don't know...!
But yes for those who are applying to schools they certainly need to connect in the right community of the people who are applying... I can bet such a messaging group can server a great purpose...! Lets have Walker comment on it... I'm sure we'll have a good perspective...!