It honestly should just be implemented into a tutorial… and that’s it.
All these ways of forcing people from not being able to repair/defuse at the same time can be detrimental to the game.
Here are a few cases where dual repair/defuse might be a good thing.
The last objective on underground can be difficult to defuse for the defender team, especially if the gates are closed, and even worse if the enemy team has pushed up and is now in a good spot to defend against any defuse attempt.
Lets say its also in overtime with only a few seconds left and the bomb is already 75% defused… whats a good strategy? What can you do at this point?
If there is not enough time to kill everyone and defuse (which is often the case, as hunting down every last person in that wave takes time), then you simply have multiple people pile onto the C4 and disarm at the same time, this keeps the defuse process live until they kill each and every person disarming.
I’ve had rounds won due to this tactic, but its all about knowing when to use it. If the enemies are making use of molotov’s or airstrikes then it can get your whole team killed in a matter of seconds… but if not then you might survive long enough for someone on your team to finish that defuse.
The same is true for repairing. Take a scenario like Bridge where you are pushing up to repair the EV. What if only 2 people make it there alive and you have a full spawn wave about to tackle you? Well If you feel confident, you can try and cover your team mate (and you should at least try)… up until you know you are going to die (low HP, no ammo, etc) then you might as well just jump over to the EV and start repairing, its the last thing you can do that might be helpful… even if it gets your teammate killed (they were going to die anyway because you could not longer protect them). At least you get a bit more repair progress done. Best case scenario though would be to communicate with your team via mic, and say you’ll take over repair so they can then cover you instead.
Know what will get you the most progress on this repair/defuse… If you have a couple of Engineers working on a a single obj at the same time, they will get a lot more progress done on that objective on average, than just one… since the other team has to eliminate both of them before the obj progress is stopped.
In the end though its all about being aware of the situation, knowing your team, knowing your enemy and knowing the game. There is always a good reason to do something, or not to do something… the problem is that most people seem to be lacking the skill/knowledge to make the correct choice when the time comes.