after checking out the prc i really gotta ask...
you get limited amount of limited stuff that looks like you do something but has no effect whatsoever...
you could do sooo much better with other classes like chameleon, urpriest, even trapsmith
factotum or pretty much anything
this sentence no verb! and Diplomacy does not allow you to cheat lie or steal so that has nothing to do with anything...
another suggestion is silverkeys prc
its dwarf specific or stoneblessed specific ;-) you can operate thiefstools at range and may pass any portals/dimension doors and enter mordakeins magnificen mansion as if you were allowed to.
and if you want to kinda backstab your party id recommend mothercyst feat
gives you new spells which are all enabled by the second level spell that besotws a undead tumor on people from there on you can hurt control detect and instakill them.
infect them when they sleep and everything is up to you from then on you can force anyboddy to do anything.
its hard to help you because i dont really understand what you wish to accomplish.
if you just want to play a pretender someone who has no ablities on his own...
MAYBE: a kensai with item famliar that way your equipment will be much more capable then you
OR :i'd also recommend fiend of possession so that you can manipulate other people and even objects
OR: a thief acrobat / exemplar if you want a burglar/trickser kind of character
OR: thematically maybe you shoud check the master of masks, fortunes friend, uncanny trickser, battle trickser from complete scoundrel