In this post I presented a Wizard class for BX that I'm using in a current campaign. I tweaked it a little and added my own art in this updated version. It is compatible with BX but definitely has more bells and whistles. Still... it's all on one page, with art and an XP table. So it's not too crunchy. I like it. I think this would make the beginning spellcaster more interesting to play. And yes, this class does in fact replace Magic-Users and Clerics in my current BX game.