Even with a TTI box the rear facing shift lever is not as smooth as the linkage type for the reason you noted.
But being a TTI box you can get away with the reverse lever without losing your mind.
What I never quite sorted was using a T160 type kicker with the rear sets and the reverse lever with said TTI.
If you use the lever on the footrest with a linkage to the gearbox, the direction of change is maintained. My TTI box came with a Triumph shift pattern, i.e. one down and the rest up.. Being a dickhead I just fitted the box and when I tried to ride the bike, it would not move. So I gave it a heap of revs and dropped the clutch. The Commando has so much torque that if you rev it, it will pull any gear. The bike took off in 5th and I almost stuck it through a fence. It had a fair distance to run, and I caught it in time - just !
I think that lever and linkage is standard on most Manx Nortons. I think Bruce simply fits the change drums which he has the most of in stock at the time.
With a kick start , you probably need hinges at the footrest and the toe of the gear change, but if the change toe is hinged . . . ? - Buy an electric start and push the bike if you get a flat battery ?