>>28765109Feint has +2 Priority, which is BIG because it means that your other Pokemon will be able to hit the broken Protect. Also, it lets Feint be a nice way to remove Pokemon who withstood a hit due to Focus Sash from the field before they can get another attack off.
Brick Break, on the other hand, doesn't have priority, so you have to make sure your faster Pokemon uses Brick Break so your slower one can attack. Requires a bit more planning.
The real problem is distribution. Feint doesn't have widespread distribution, which helps in it not becoming ubiquitous. But everything and it's mom can learn Brick Break. It'd be Knock Off 2.0.
If they did this and then nerfed the power to, say, 40 BP, it wouldn't be so bad.