Actually, you already answered that question. I should read the thread.
1) It will encourage PC's to have lower high ability scores, but it doesn't follow that, for example, a Wizard who cannot get a +5 Tome of Int would buy a +5 Tome of Wis instead of Pearls of Power or staves or similar. It seems more likely that highest scores will be lower and low scores will be unaffected. Why is this a design goal, anyway?
2)+34 to hit is ok for attacking a Balor, with AC 35 (really 39 due to at-will Unholy Aura) means your primary will hit on a 5. But your secondary needs a 10, your third attack needs a 15, and forget about your fourth attack. The wyrm black dragon also has a 39 AC. Is hitting with about two attacks a round in melee really enough to stand toe to toe with a dragon's 46/41/41/41/41/41 attack routine? That's a slugfest that will only end one way: pureed PC. That's not really your fault though, Dragons are murder machines. Consider the Balor again. It swings at only 31/26/21/16 with a vorpal weapon and 30/25 with a flaming entangling whip. Hey, that whip calls for a Str check to resist it. The Balor has a 35 Str. Our 20th level fighter with ability caps cannot have more than 29 Str after a +6 item.
tl;dr You can hit once, but iteratives are hindered, and one attack a round at high levels is pretty garbage.
3)What saves are based on secondary attributes? Full casters are all SAD in core, and save DC is a plenty good reason to boost an attribute for MAD casters like Favored Soul. Paladins and Knights and other Cha-influenced brawlers would like more Cha... but removing options isn't the best way to encourage variety.
You don't have to be a wizard to stun. Monks can do it, there's a Sudden Stunning property in DMG II which Cha-based melee characters like, Clerics and Druids can probably stun thanks to so many spells to choose, some fighting style feats allow stunning, and the list goes on. Choose an affliction, and there are probably many ways to induce that in an opponent. Look at fear/intimidate optimization and you see the results of a condition track.Except that if everyone plays a wizard so they can spam stun, they'll be extremely vulnerable to classes and monsters that are strong against wizards, and they will find themselves having to escape or face a TPK relatively often.