These classes have odd, disconnected requirements (e.g., scattered skills, irrelevant feats) that clash with their archetypes and newer base classes, hindering roleplay and mechanics. Rewards feel like "rebates" for buy-ins, delaying engagement.
I propose streamlined requirements: 5 ranks in a spy skill (Leadership, Intimidate, Bluff, Perform), 1 relevant feat (also as a pool but relative to the archetype the PrC counts as), and PrCs counting as represented classes for features, focusing on roleplay over mechanical payoffs. The rewards for the buy ins should a class+ where you are just a sneaky (socially, not always actually) fighter, mage, or whatever.
I would love to see the 5 levels count towards progress where relevant in my class - for example were I to be a warlock harper/naugadar I could still get my "capstone feats", or a paladin taking paragon was just treated as taking more paladin, and any caster that was 20 (class) / 5 (casting prc) was considered an epic caster for feat qualifications. Cleric paths don't apply where it makes sense fear speaker/priest, or things like evangelist w/ master harper.
Anyway, thats all I have to say.