DM Stalwart - in line with your post above about not wanting to be weighed down by new mechanics and such... I thought it would be prudent to do a partial suggestion first before writing up a full blown character.
Medium BAB, Good Fort and Will saves.
4+ Int skills per day, with access to all Knowledges
6 level spellcasting based off of Wisdom
Primary defining ability is to be capable of manifesting a Phantom (similar to an Eidolon)
Phantoms are partially customizable, but only in choosing an 'emotional focus' - which for my character would be Despair. This gives his phantom some emotionally based abilities (such as increased attacks vs shaken / emotionally compromised targets, Aura of despair, etc).
A 5th level Phantom would be a 4 HD, +4 BAB, 8 skill points, 2 feats, with 2 x 1d8 slam attacks.
Phantoms can either manifest as 'incorporeal' or 'ectoplasmic' = physically present. Each form has different advantages and disadvantages - though my character would focus predominately on the ecto form - as that's the one that can most easily attack.
The high concept for the character would be a Half-Elf that was brought up by his elven mother after the human father abandoned her. His mother sank into despair after the abandonment and subsequent shunning by the elven community, eventually giving up and starving herself to death. My character then lived hard, suffering through whispers and voices eating their way into his head. Eventually learned the ability to summon his mother's essence as an emaciated phantom.
From there he pursued and ended his father's life, and came to the attention of the Red Mantis as a piece of unmolded clay. Since then he has been shaped under their care and grown into the level 5 operative he is today.
If you could give me a small indication of whether there is enough of a piqued interest to see a full blown submission that would be grand :)... or if the potential of learning the rules puts you off, feel free to tell me no as well.