>>95898419
>player’s companion book is buildfag central
You mean the custom class rules right? If so, I'd consider them the opposite of buildfagging.
Buildfaggotry is when you can pull shit like 'Oh I'm going to take 3 levels in Fighter, then cross-class into Klansman for the Bigotry feat so I can use the synergy between that and the Hatecrime subsystem for an extra 3d6 Vile damage every time I tell someone to bite the curb before attacking'

Custom class rules are entirely GM facing and just there so you can create shit for your own settings, with each class being its own, separate path that outside of a few exceptions doesn't really get choices past which class you want to be.
Could they be abused? Sure, if the GM is fool enough to tell players they can use them.
But on the other hand if it lets me, as GM, do an entire group of classes for, say, an Arabian Nights setting
>Dervish to replace fighter
>Bandit to replace thief
>Astronomer to replace wizard
>Imam to replace cleric
>Rider for Explorer/Barbarian
>Maybe a few 'secret' prestige classes that their characters can convert to if they stumble across them in the world (Demon binder, Palace Guard, Hashsassin) which'd trade more abilities for slower XP growth if I'm feeling quirky
With all the little tweaks I, as GM, want to put in there?
That's a cost worth paying far as I'm concerned.

Just don't be a retard and let your players have their hands on them same as you wouldn't let them get hold of monster abilities.