So at lot has already been said and written about the SL and advantage systems in 4th ed (and I totally understand why you find it frustrating to keep track of things - that was my main reason for never switching fully to 4th ed). But here are some specific comments to the changes you are doing: 1)...

I had a test run with my group for WFRP 4th and the SL combat system did not work as it required too much effort to track. So I crafted a simpler system where I changed SL to something called "Momentum" (you have it or you don't) and had the to hit rolls be affected by the opponents skill....