Teleport would be more interesting/balanced/interactive if killing the ward/minion canceled it
The cooldown and channel time could be significantly reduced to compensate, which means more teleport plays and interaction between all areas of the map. Just make it so the enemy can always kill whatever is being teleported to. You could even allow blue trinkets to be usable for teleports since they would be an extremely risky choice as they only have 1 health. This opens up many more possible plays for both the enemy and ally team. Things like enemies using flashes to get in range to kill the ward before the channel goes through, allies using heal spells on a minion to keep it alive so the channel completes, etc.
The one downside I can think of is that nearby teleports for a Baron steal would be extremely hard to pull off. I think there could be other ways to preserve this though. Maybe like a rune or item that grants double health to a stealth ward on a 90 second cooldown or something. That's just off the top of my head, I'm sure something better could be thought of.