So, I built a hybrid between 4E and 5E that works pretty well. I had originally taken some concepts from PF2 as well, as I thought they'd add just the right amount of spice to the overall mixture. I was wrong. My players, thankfully a very resilient bunch, tossed the PF2 bits on the ground and stomped on them.

I haven't had a chance to actually play unmodified PF2, so I can't speculate how much it'd be attractive to the 4E crowd... by the responses here, it appears pretty hit or miss, though not because of similarity, but just system differences.