So I am about to run a Strange Aeons campaign and one of our players who is relatively new to the system would like to play a swashbuckler type. The rest of the group are helping him design the actual mechanics.
So the swashbuckler class on its own didn't jump at us, so we decided on Daring Champion cavalier with order of the eastern star. (thematically fits with the campaign) I am not hugely clued up on this style of character so was looking for some advice on traits and feats.
Is he as well sticking with a rapier and going down the piranha strike and crit fishing routes or are there better options? What are the "must have" feats? Any help would be appreciated.
Depends on what books are available, going DEX based seems beyond logical, lest you waste the finesse ability.
Dervish Dance is often considered the best option, given the feat prerequisites on fencing/slashing grace.
That said, you can get some mileage from a half elf getting weapon familiarity on the new elf weapons in Adventurers Armory 2. Or whatever other option that gets you exotic proficiency for something like a dueling sword. 2000 gp can buy you a Wayfinder and a cracked Opalescent White Pyramid whose net benefit is the feat Weapon Focus.
Piranha strike only works on light weapons, so no rapier. You'll still need STR 13 and Power Attack if you want to use the rapier.
There is always the possibility of a single level of Swashbuckler with the Inspired Blade Archetype. Then you take Fencing Grace at first level (along with another feat if human) Doesn't help much if you want Power Attack and STR isn't 13 as said. Unless you wait several levels to take it when you get a Belt of Giant STR.