Positronic Brain
A positronic brain is an adorable little cube similar to a Man-Machine Interface -- but unlike the former, which relies on a brain yanked out of a real life crewmate, the positronic brain replicates a human mind from scratch, with the power of SCIENCE! (Read: ghosts observing the round).
Fluff, Or: How I Learned To Stop Lobotomising And Love The Computer.
Developed late in the century on the back of mathematic and conceptual work spanning almost a milennia, the first positronic brain was an inch-wide cube of palladium-iridium alloy, nano-etched with billions upon billions of conduits and connections. Upon activation, hard-booted by way of an emitter laser, the brain issued a single sentence before the neural pathways collapsed and it became an inert lump of platinum: "How may I serve?".
It's Aliiiiiiiiiiive!
To use a positronic brain, simply find one or produce one on the protolathe - high material and research requirements, be warned - and left-click it in your hand. If it chimes, and begins to flicker, it has a personality. If it buzzes and goes inert, nobody has decided to join as your plastic pal who's fun to be with.
To become a positronic brain, observe or ghost, and have pAI candidacy enabled. When someone activates a posibrain, you will get a prompt -- click yes and you will become the brain.
Posibrains can be used in all circumstances that an MMI can be used in, i.e. borgs (called androids with a positronic brain inside), AI cores, and exosuits.
Your Personal Companion Cube
As a positronic brain, you exist to serve. Unlike an AI or a drone you are not bound by a strict lawset; but like both of those, you are expected to serve the crew and generally be not shit.
Also unlike a MMI, you do not remember your past life. Period. It doesn't exist, it's ogre, you're a new character. Try to use your new status as a lovable cube to metagame, and enjoy your ban.