I would suggest you say no. My players try this occasionally. I say no because these classes are not balanced against D+D stuff.
1. Courtier. No. If you have an urban game it'll blow it right out of the water. (+ 4 on all charisma-related checks?) If it's anything else it'll be more useless than a frog in a dune-buggy-across-the-desert race. It's skill points ignore standard D+D but they don't get very many other than social ones.
Depends on your game. But I'd avoid it if you plan to adventure. If you plan to intrigue, this'll hog the limelight. Caution on the wealth as well.
2. Noble. Not bad. Good for a charming and witty pirate leader or what not. It's like an unmagical yet good bard. Only problem is it's leadership stuff but that depends on your campaign. Just substitute with a bonus feat. I don't mind this one apart from its starting riches - which in D+D means a lot more than in Swashbuckling.
3. Pirate. It's powerful, almost stupidly so. It basically gives you a lot of minor tricks. Drop the base attack to a rogue and the hit dice to 8. It has two good saves and 4 skill points and the abilities often make up for the lower base attack quite nicely.
4. Spy. Same issue applies here as with the courtier for one thing. It's basically a rogue that is slightly more urban focused for half the skill points. I'd recommend against it and put the rogue in it's place.
5. Swashbuckler. For the swashbuckling game I raised both the hd to a D8 and skill points to 4/level. Nonetheless, it's a suboptimal class; it's entirely designed to hit prestige classes I assume.
Never tried to change the highwayman. You might try duel crossbows. Replace Quick Reload with Rapid Reload and you might be right. Make sure to only allow light crossbows until 13th level when they can use double musket. Replace with heavy crossbow.
The musketeer doesn't look bad to me, btw. One way to do a swashbuckly paladin sort.
Also, unless you are really, really sure, avoid prestige classes like a plague of horrible space rats of doom. Some are hideously powerful (And I'm not talking about The Chosen One or the Evil Pirate one.)
Swashbuckling Adventures is balanced (mostly) against itself. The way it works against a standard D+D adventure - your characters will probably blitz through humans (Conversationally or otherwise) and die hideously to something with lots of hitpoints, low AC and high damage potential.
Oh, and be careful of feats. Some might do things you like. Others might well change the whole combat dynamic.
