I think if I were trying to lose the stoker cranks, I might get a couple of beater grade drive side cranks off of aliex to maintain the existing crossover drive and saw the arms off to clear the pillion pegs. Doesn't even matter if you end up with a non-unity primary drive ratio, and you might even exploit it to adjust the overall gearing.
I thought about that, but then discounted it due to the nds stoker crank. But getting two of them is a good solution, and the incorrect pedal threading is irrelevant because they've been cut off!
No, that's the extent of it.
I think if I were trying to lose the stoker cranks, I might get a couple of beater grade drive side cranks off of aliex to maintain the existing crossover drive and saw the arms off to clear the pillion pegs. Doesn't even matter if you end up with a non-unity primary drive ratio, and you might even exploit it to adjust the overall gearing.