pogre
Legend
I kind of love this idea...Even more simple and for me a much greater impact tan opportunity attacks, re-roll initiative every turn. Randomness/chaos this adds to combat is awesome. PCs never know if they are going to get to attack twice before the BBEG, or if the BBEG will get to go again before they can. If you let it impact spell durations as well the chaos is even more significant.
Interesting combats, imo, are about variability, and for me, the easiest way to do this is to re-roll init each turn.
I run a pretty big table though. We pride ourselves on fast paced combat. How much has it slowed you down? Do your players get frustrated by the rule?