This is an excellent place to note the remarkably readable dragon article on "Reflavouring powers"
With an understanding between you and your DM, you can call most any class "Swashbuckler" and, moreover, have an appropriate style on the battlefield.
The best light-armor defender is the Warden with abilities that allow her con or wis to be used instead of dex for AC. It's even quite effective to reflavour the class to be nautical and rapier based.
The rapier as a military light blade, is now part of the warden's default proficiencies. The best buckleswashers will be lifespirit or wildblood. Consider the following:
"Polly was on her knees, breathing heavily. A long gash marked her forearm, but she was smiling, for she knew something the enemy didn't know: where there's life... there's hope! With an inspiring shout of glee, she wrapped her torn shirt around her arm, and swept her rapier back off the deck. Her comrade in arms took heart from her indominable spirit and waded back into the fight"
Mechanically, that's a second wind, with a free surge use handed to someone else. Flavourfully, there aren't any spirits around.
Warden's Grasp, the ranged II of the warden:
"Polly grinned, and with a quick flick she looped a coil of rope around the dunce's arm and gave a tug. As he staggered backwards, another flick looped the coil back around her forearm: a rope was such a handy thing in a battle."
The daily forms would be a bit more difficult, but the same theme can easily be applied with some thought. The protection and difficult terrain of form of winter's herald could be a rope thing, or maybe she can call on the sea in times of need. Maybe it was some ancient bargain she struck with a rescued dolphin.
In summary: reflavouring is powerful, fascinating, and requires thought. Start with the mechanical requirements, see to what class they most easily apply, then reflavour to suit your needs in consultation with your DM.