I'm mostly against switching systems when I like the one that I use but there are 2-3 things that I'm going to change to make it even better.

I do not want to learn an entire system because I want to dodge modifying the few things that are bad in 5th.

As for the rule, my dear friend, you completely missed why it exists in my game. The reason is simple to keep my players engaged and entertained even when they are at 0 hp. That's it. nothing more and nothing less. It's not because 5th has bad exhaustion (because I never used it in my game to begin with) and it's not because being unconscious is boring (when not using my sweet condition) that I'm going to spend hours and hours relearn an entire system.

I'm fine with 5th. I like it. I'm not going to change cars because I do not like the paint color. I'll just repaint it and enjoy it then.