AndKenneththesupremecommanderBased on research I've done on client plugins (and coincidentally for fixing the pause bug), I can confirm that it IS possible to replace player names on the HUD. All that's required is figuring out how to pull Steam ID info on the client-side, which would be the best way of identifying players uniquely.
Do you get the steamID as part of the client when watching a sourceTV? Otherwise, you could do an a2a request to the server itself. Not the most elegant, but it would get the job done.
There should be, given that the client receives Steam information as well in order to render the HUD (especially the scoreboard and the avatars on it). I'll continue looking into it and hope to come up with something concrete soon.