I really like the sound of the game mode. The player who is tagged should lose there speed and have to build it back up again. I think they should also be frozen for a second or so to stop them insta-tagging someone else. I think you should be able to push players but not the one whos it (this also goes for the second mode i mention below, tagged players shouldnt be able to push, but untagged can push... "save yourself *pushes dinius away from taggers while i get frozen and tagged*) .
As for visible on the map i see a few game modes.
Firstly, I see a game mode where 1 or 2 players are It and they then hunt the others. On tagging a player, the first player no longer becomes it, and the second player becomes it. However, what is the win criteria on this mode? I don't think if its 1-3 vs many a way to find other players is needed. As there should be enough other players to find people (maybe make it so that < less than 5 enemies you get some way of knowing where they are?)
The second mode i see is a kind of "infestation" mode, 2 players start out it, and they have to tag every other playe. When they tag another player that player becomes it but the first person doesnt become normal, they are still it. This way eventually one person will be left, last person is the winner. As this gets to a low player count, some identifying way to find hiding players would be needed so again, maybe < 5 people left display a way to find them.. Otherwise people might just hide rather than running / freestyling around. Maybe in this mode, the person who is tagging should also be slowed / frozen for a moment so that they cant just multi tag 10 people at the same time (for this i think a slow would be better than a freeze)