If you're trying to add more than a certain percentage of your realm to a message group, to the point that you're hitting the message group size limit, then you really need to be asking yourself, "Why does this need to be a message group? Why am I not just sending these messages to the entire realm? Why am I deliberately and repeatedly excluding a very small number of realmmates from these messages?"
If you can give me a very, very good reason, that is not due to a highly specific weird thing you're trying to do with your realm, but generalizable, I will consider adjusting the message group size limitations.
