A widow or hanzo, maybe.
But that’s not really an argument. “Do this because I can die in the same amount of time or less?” Not really compelling.
After a dozen or so hours in this game, I have never had an issue with deciding if a junkrat trap is friendly or hostile. It’s really not that complicated, unless, as ChibiFox said, it’s on stairs.
I’ll give you that one. Junkrat trap is terrible with stairs, friendly or enemy.
You’re focused too much on the trap being an ally’s. I would consider it a design feature to require actually paying attention and deciding whether or not the trap is safe. Adding a super clear indicator to the friendly trap will ruin one use of Junkrat’s trap… causing the enemy to pause for a split second to look at it and then shoot it. That can give you an advantage. If you fall prey to it, that’s on you.