In 3.0 I played a highly effective Fighter/Wizard/Spellsword counterspelling mage from level 1-16, so I have a few good tips.
Your feat path looks pretty good, go with it.
As for spell selection, I highly reccomend not specializing, or if you do specialize, to specialize in Divination. Having a high-level spell for each school is handy with improved counterspelling, also, look out for spells with long ranges, as they can counterspell farther away.
Playing a sorcerer might be a good idea, because you really can run out of spells doing this whole thing pretty easily, however, you can make some BBEGs look pretty stupid when they can't get a spell off. My personal favorite was blowing conjurations to keep the evil clerics from healing their masters.
As far as class selection:
With improved counterspell, I don't see much of a need for going Mystic Theurge, and let me tell you, Improved Counterspell works MUCH better when you are on the cutting edge of spell levels for your ECL, as a multi-classed wizard, I was frustrated with my lower Dispel Magic rating topped with my lack of highest-tier spells.
Pro-Wizard/Anti-Sorcerer Arguments: A straight-up sorcerer has the disadvantage of getting the higher rank of spells one level behind, so that's a big plus for wizards. Also, the ability to add any spell to your book can really help when you know which enemies you are facing, and what their favorite spells are. Recurring villains robbed of their signature spells get very mad very quickly.
Go Archmage!
Finally: Any chance you can run a counter-spelling cleric? It could work very well too!