I don't see how this differs from any other communication app except being centered around Blockland. At any rate, this was a terrible idea to open this topic without any progress or concept art that you've made or anything; all you've presented to us was an idea. Literally anyone can go and steal this idea from you and make it come to life before you can.
I'm not trying to discourage you, but it's a bit disappointing to see that you've came up with nothing at the moment. So, if I were you, I'd close this topic right now, and get some work done before you start a discussion about it