I think it might be more balanced for an AI brain transplant to wipe their skills to a base level and make them incapable of social and maybe art and research (but capable of everything else, no matter their personality and skills when they were alive), with no passion in anything. Maybe even make them not have moods or relationships with other pawns, and give a mood debuff to their friends and family when they see them. I would also make them incapable of improving their skills or having skills degrade; maybe better quality AI brains could have better skills. A poor quality brain might have level five skills across the board, and an excellent one could be level ten across the board. I can think of quite a few scenarios where this would be interesting:

Levin, a popular colonist, has just been outfitted with fancy bionics, which were a real stretch for the colony to afford. While out taming a muffalo near the edge of the colony, raiders attack, and he's shot in the head before he can make it back to the safety of the walls. The doctor is able to save his body before he bleeds out, but his brain was destroyed. His wife and son want to give him a proper burial, but the colony is badly damaged and lost most of its builders in the raid. Even a small raid before repairs are complete would likely mean death or capture for everyone there. The doctor keeps his body alive in the hospital for a few days until a friendly caravan arrives, selling a bionic brain. After selling his bionic arm and the last few sculptures he made before the raid, the body is soon walking around again. However, Levin is gone. He's technically competent at most things; he can even cook a bit, which he was lousy at before, but the brilliant artist who brought so much joy to the colony is no more. His healroot garden, which he took so much pride in, slowly dies, as he's not quite good enough to keep it alive anymore. Maybe more importantly, his family can't ever get over his death, because every day, they're forced to look into the emotionless eyes of their dead husband and father.

A war caravan has just safely returned to the colony, carrying the spoils of a successful conquest of a nearby hostile tribe, which had been harassing them with constant raids. Among them are three prisoners whose injuries happened to be serious enough to incapacitate them during the fighting, but light enough to be treated in the field by the combat medic after tending to the colony's own wounded, and whose skills would be useful to the colony if they could be convinced to join. After weeks of schmoozing with the warden, two eventually joined and became useful members of the colony. The third, however, is stubborn, and the colony can no longer bear the waste of food on a hopeless prisoner. Even though he is skilled in medicine, they conclude that there would be no point in trying to persuade him. However, there are sunk costs to consider. The doctor is capable of removing his organs to keep in case someone needs them later, but there's a heat wave, and it's not certain that they wouldn't rot. A trade ship happens by at the perfect moment. The colony is disappointed to find that they don't buy slaves, but they happen to have a basic bionic brain for sale. They trade some of the loot from the tribe for it, and the doctor goes to work. Some of the colonists are unsettled by what they've done, and a second doctor would have been a real boon, but there is no argument when it comes time to haul garbage or chop wood, and there will certainly be no tears when he falls leading the vanguard on their next raid.