aramis erak
Legend
I feel you're getting hung-up on labels. It doesn't matter if it's called a rogue or a fighter, what matters are the results.
I agree with you that Thieves' Cant sticks out, and I'd prefer a way to do without. But skill monkey? When was the last time we saw a swashbuckler character who wasn't athletic/acrobatic/silver-tongued? Skill monkey makes perfect sense.
I'm not saying it can't or shouldn't be done as a fighter, just that--to me--rogue is actually a better fit.
You're showing a bias towards the Musketeer period duelist...
But duelist also applies to certain 13th and 14th century judicial champion types, and to certain others of that ilk. It also applies to many Celtic tribal types, and some "Viking" types. All of whom tend to be far less multi-talented, and far more single-weapon or sword-n-board types, in chain or bezanted.
And it also can be applied to the gladiators.
It can even apply to the Jouster, tho' he's as likely as not a different sub-class of fighter... the Cavalier.
For those types, a fighter subclass is a better fit. Only for the Musketeer era is the default character a wise-cracking skill monkey as portrayed by Alexandre Dumas and his imitators.