Needed a pole for a new hull I have on the way, its not quite finished but heres what solidworks + mastercam + a cnc can get you combines a few of the concepts I like from poles on the market atm.
I just read this entire thread, very interesting. Are you set on the under mounted steering? I feel like under mount steering is more susceptible to loosening, wearing out seals/o-rings and loosing tolerances due to the added stress of the rider exerting downward force on the turn plate & steering system. I feel with top mount systems, the main force is the push/pull with downward force being lessened by the turn plate and steering system "sitting" on the pole itself.
If it is designed correctly then there should be no problem with loosening of any nuts. How this design will be I have no ides but it will not be compatible with stock SN turnplates. I'd love for it to be compatible with any aftermarket one but if not then I'll just make my own.