Mesaana was apparently already in the WT in TDR, when Tsutama was still in her exil (IIRC). Why should Mesaana begin to play Tsutama that late, if she didn't have the need before?

Besides that, you don't explain why Alviarin thinks that Mesaana's true appearance & voice are familiar. And why Mesaana wants to kill Alviarin, after she saw Mesaana's true self, if Mesaana is playing Tsutama? (who as far as we know, doesn't look like Mesaana at all and even has the ageless face).

Finally, there is this Q&A from after KoD:
Q: Mesaana: Do we have enough clues to know her identity?
RJ: I think so, but I'm not absolutely sure. Her Third Age role has been at least mentioned.

I wonder, if "role" mean in this context her general role like AS, Accepted, novice, maid, secretary, servant or clerk, or does role actually mean the concrete person Mesaana plays.