This "analysis" doesn't consider the context of the offenses across MLB during the time these players played. If you do (and you only consider guys who had been the Brewers 1B for 3+ years) and you look at something like WAR, the order should go:
1. Cooper
2. Scott
3. Fielder
4. Sexson.
beyond that, there were several guys who had one excellent year as a brewers' first basemen, but Greg Brock shouldn't be in the top 8 (his peak WAR was 1.8, and his other years were much worse). If you forced me to pick a 5th, I'd take John Jaha.