The only obligation a pilot in command has: is to inform the controller that you are going to deviate. It is not required to supply parameters of the deviation or even of the direction of the deviation. By asking for permission to deviate you are giving the air traffic controller your command authority. NEVER allow an air traffic controller to take command of your aircraft.
And when you have the mid air ... let's hope your family can pay the legal bills.
If you need a deviation, as several level headed posters have said, let us know as soon as you can, and let us know what you want to do. 100% of ATC will try to help you out.
If there's a reason we can't approve it, such as 5 other aircraft have already gone in to that clear bit of sky, we can let you know and give you some other options. If you still want to go there, we can give the separation responsibility to you and your TCAS. Our game ends ... yours just begins
The lawyers will win again.