It's pretty easy to swap that solenoid pack. It'll take you around 2hrs and cost you $250 (plus filters/seal/fluid if you do those then too).
My sensors are all accurate and I've never seen any sporadic readings when logging, so I think it's just code.
I do agree though, and looking at the solenoid pack, I really think a stand alone wouldn't be the hardest thing to make. The tough parts would be:
1) Adding a learning feature to understand clutch thickness since there's no bands to be adjusted.
2) Adding the logic around temp and how it changes fluid characteristics.
3) Making it in a way that people couldn't apply the wrong solenoids at the same time and burn that thing up fast.
And I'm pretty sure 4th gear is part of the direct pack, not the OD pack. Also, your OD pack should be the larger billet one that addresses the low torque slipping issue in 5th and 6th.
Filters/Seal I got:
Seal & Both Filters, 68RFE
Solenoid Pack:
Newest Rev OEM Solenoid Pack, 68RFE
Procedure Video:
45RFE 545RFE 68RFE Shift Solenoid Block Pack Replacement - Install RFE - YouTube
:Cheer: