100% not optimal, totally get that. It's a flavour/RP-ish thing.
It isn't the inspiration for wanting to do this (just thought it would be cool to wield both after seeing the synergy in the weapons) but are you familiar with Gangplank from League of Legends? Effectively that. He dual wields a cutlass and pistol but is considered a melee character entirely, auto-attack wise. He has an ability that uses the pistol from ranged but otherwise you can think of the pistol attack as just an alternate animation that accomplishes the same thing as the cutlass animation - it looks cool but it doesn't actually 'do' anything, in that specific instance.
Another example of the fighting style I'm trying to replicate in-game would be some of the pirates from Black Sails - probably most notably Blackbeard. He's strapped with multiple, single-shot pistols across his chest while also wielding a cutlass.
It's a little clunky but the Black Jacket weapon swap setup makes me curious. It would be a slightly different way to put One-Handed Style, too (pity that pistols are two-handed in PoE1).
Thank you for the ideas and feedback! I appreciate it a lot.