Now that you mentioned it, I see that using different messenger in the later level have very little to no effect, where there's enough people to the point that it doesn't really matter. We will keep it in mind.
Thank you for the detailed feedback. I think you really got us important points to consider!
p.s. I mean really really important point (the core of the game!). If you didn't bring that up I would surely won't notice it. I'm very thankful for the feedback. ^ ^