Aaron, why is an INTELLIGENCE based gish "commoner"?
At the moment, the only viable gish is a muscle wizard.
Why? Because dispels will murder you if you don't have 30/29 Cl.
Wizard15/EK10/Swashbuckler 5 gives you 28 Cl. It's still somewhat acceptable, but your damage is miniscule compared to a muscle-wizard due to no access to IPA and piercing damage having the most frequent DR against.
Now, you want to play an intelligence-based Bladesinger.
Wizard 5/bladesinger 10/EK10/swashbuckler 5.
Your Cl is absolutely non-existent. You can no longer ward with hopes of keeping your wards. You need something to dodge dispels.
Wizard 12/shadowdancer 3/bladesinger 10/Swashbucker 5.
Finally - you have it all: damage, AC, avoiding dispels and damage. Your BAB is miniscule compared to the muscle wizard. you are now a MAD character like a paladin. Your Cl is practically non-existent.
Intelligence based bladesingers are one of the intended designs, seeing how they can do rapiers and longswords both. And how Song of Celerity encourages offensive spellcasting - which relies on intelligence again.
My character, a wizard17/duelist 5/shadowdancer 3/swashbuckler 5 is practically an after-market intelligence based bladesinger. No levels in BS because of RP. Has 2 points less BAB than the bladesinger would have, 1 less Cl, 1 less AB, same damage (or more, if going duelist 6), more naked AC, no need to wear armor, more free feats, way more dexterity.
Intelligence based wizards are forced to take swashbuckler 5 for equal damage to muscle wizards, reducing their Cl 5 (or 1, with practiced).
Consider this.
The more intelligent caster has less Cl by STANDARD than a muscle wizard. It's more less even when you optimize a muscle wizard for maximum damage and melee potential (29).
This means the more intelligent arcane warrior who is optimized for damage and melee potential (the Bladesinger build) has just a whooping 8 less Cl than "more muscle than brains".
This means their spells last way less and they've no incentive to take Extend spell - seeing it will just get dispelled over and over again.
So they don't have extend spell. Meaning, their spells last less than their rest timer does by default.
They're also Bladesingers, who have Song of Celerity. Meaning by lore and design, they're supposed to use spells offensively. So even less room for warding, at cost of offensive spellcasting.
As an added bonus, intelligence based gishes are an absolute torture to play before level 23.
As a second added bonus, int based bladesingers can barely loot. By needing armor, unlike the duelist variant, they always carry an added weight of a mithral chain shirt. By being MAD, they can't afford to waste points on strength - since strength is literally useless beyond carry capacity. Even charisma is more useful than strength due to UMD - but you could instead invest those into int/dex to be better able to match the muscle wizard who has no such sacrifices to make.