I haven't actually tried this out yet but I believe this should work.
Start with a sorceror. In addition to having Improved Counterspelling and Reactive Counterspelling, make sure to get Heighten Spell. Since Reactive Counterspelling allows the use any spell of a higher level of the same school to counterspell, Heighten Spell is invaluable. Make sure to have a variety as far as schools (especially 0 level ones) so that you have a spell from each school and thus take advantage of Heighten Spell.
Hope this makes some sense.