The issue with a pk being a penalty is that not all fouls are created equal. A hard dogso leading to injury is very different than an unintentional handball that doesn’t stop a goal scoring opportunity. If you throw a header rule on top of that you have even more issues. One way the refs differentiate now is to ignore quite a bit of it such as the shenanigans that go on now with corners (such as shirt pulling, pushing, impeding the gk, gk making contact with a player). I’ve even seen refs take fouls they whistle for that occurred in the box and move them out for a dfk. Differentiation of these fouls would require something more drastic than just allowing the gk to move: now we are talking either point differentiations or something like the idea of treating some of these like dfks.