Group Messaging needs to grow up.

I recently developed the need for a real time group messaging system that allows the members to subscribe to topics and tags. Posting messages in such topics or including such tags would then result in a push notification to the subscribers mobile devices.
The admin of the group could create a taxonomy for the groups context, and members could contribute to the taxonomy, based on an approval system.
This allows for subscribers to carefully decide themselves what messages they want to receive, instead of somebody else deciding for them that they are interested in.

You see, because I hang out with a loosely organised group of artists, freelancers and randomly creative individuals, we need a tool to be able to mobilize each other, but only the people interested in the joint venture at that moment. So we want to create a list of topics/tags and locations to subscribe to. We want to keep informed of only what we subscribed to. The group is just too large to blindly spam everybody with every message.
And since we are often in the pre-organising fase, we simply want to be able to tweet a message including one of these tags to elicit interest and motivation to those possibly wanting to cooperate.
Not only that, sometimes we simply want to mobilize a group of individuals to meet at a certain location. Last minute spontaneous action.

Well, after doing some research I found some great and promising startups in the group messaging industry, as that industry is taking off like storm.
I really like the irc-like Convore, and posted my feature request there, but no answer yet. Too bad none of the tools I looked at (Beluga, GroupMe, Kik) offer what we need. Sure, there are some forum-like tools that send you an email when somebody posts in a thread, but none of these tools allows for subscribing to a taxonomy. Please correct me if I’m wrong.
I think most of these tools are truly helpful after the fact of organising structures. When all the roles are defined, the players are known, and from there it’s just a matter of communication and collaboration.
Not what we need.

So, because I am a programmer, and therefor lazy by nature, I want to appeal to the group messaging industry first. By asking them to incorporate such a mechanism in their platform, so I don’t have to build it myself.