Power seats with memory functions use the PCM???
I woulda guessed that they would have a dedicated controller separate from the PCM...
If you really want the memory functions, you could probably get the PCM from the same vehicle the seats came out of.
Keep your original PCM as-is for everything else but add the 2nd PCM for the seats...
Connect the 2nd PCM to the seats and to 12 volts supply, and
mount it under the passenger seat or somewhere.