In python we could catch some interesting Blender events, like file saving or scene modification to automatically export the meshs of the scene using object names or layers.

That's not to say that this wouldn't be very cool. It definitely would. However, I think there would be a better solution than that blender real-time exporter. If you have a look at the tools that Eskil Steenberg wrote to make his semi-mmo game "Love". His tools are all open source and freely available and use the Verse protocol.

Again, to add this to the main engine code would be a strain on the design, however, when the plugin system is set up again, might be a candidate for that. Not that I have time to do this, but I thought I would just put the information down in case someone else was interested in picking this up.