You seem to be missing the point.
A Wizard/Archivist MT build is a better base for Geometer, but even having the casting stat be Int for a dual classed caster still does not break it even if the progression goes up to level 20.
Having 17th level casting just isn't impressive at level 20, even if it is in two different classes. You lose out on peak power in terms of more versatility and endurance. This is at best and even trade but more often is not.
Comprende?
Except... at 17th level for both classes... you really don't.
What's the difference between a 17th lvl Wizard and a 20th level wizard? Aside from the familiar...
3 9th lvl Spell slots, 2 eighth level spellslots, and 1 7th level spellslot, and three caster levels.. of arcane spells.
Those spell slots are nice... but you're gaining 2 9th lvl Divine spell slots, 3 eighth level divine spellslots, and 4 7th level divine spell slots.
This says nothing of the increased saves, hitpoints, BAB, and skills.
So your 20th lvl Wizard has a base of 4 9th, 8th, and 7th spellslots...
My 17/17 Wizard/Cleric (Geo) has a base of 3 9th, 5 8th, and 7 7th lvl spell slots.
So, you get +1 9th level spell... I get increased hitpoints, BAB, Saves, Fully armored arcane spellcasting, access to Divine Metamagic feats (and can use them on my arcane spells, I believe), and full access to the cleric spell list... and I really only "need" 13 wisdom because I can buy a +X wisdom item by the time I hit high enough level to need it.