I like your oUF_Simple since it is... simple yet informative, the same philosophy I used for oUF_lumen.
Only suggestion I have is the debuff filtering like you suggested. On oUF_lumen I use a white list for important buffs and debuffs self applyed by me, the rest of the debuffs I simply gray out the ones that are not my own. I don't believe anyone has time during a fight or PvP to go through an enormous list of debuffs to see what is present or not anyway.
You can see what I mean in this image:
http://s.cdn.wowinterface.com/preview/pvw44951.jpg