Something like a mist similar to Hextech Sweeper that allows you to see the bush. It probably won't reveal stealthed units and it could start at 120 seconds into the game to prevent using it during the level 1 skirmish. Also, it could have a "one every 5-7 minute" cd use to prevent vision spamming.
I personally think that adding any vision to TT would potentially lead to a very stale game. That map would be so easy to ward for. That's not to say it wouldn't also benefit from vision. It's currently pretty random and snowbally. This is a hard design problem. Adding a single element to a complicated situation we don't fully understand is likely to cause more harm than good. If we wanted to do something here, we'd probably need to attack TT more holistically and find out what we want good gameplay on the map to look like.
