Countless times I've needed to message everyone in my guild about something or to notify them. It is the most Direct and effective way to reach out.
Yes we have chats
Yes we can message each individually
It just is not effective and is a waste of time Not to mention some things get buried in chats quick.
Even if there is a limit to like 10 at a time or something that is heaps better than single messages.
Reasons for this are endless but:
Needing to tell everyone about something we are planning. Events, me making free sigs for everyone in the guild and to tell me what images/colors they want, ill be afk for 2 weeks because I'm on a detachment
All I'm saying is it would be really helpful and I honestly see no reason this wouldn't work out.
It can obviously be a new privilege that can be assigned etc.