Though I'd dig this up again.
I've gone with the pillion pegs for just now on the basis that it cost me nothing but time, paint and some fasteners to get them cleaned up and involves no fundamental alterations to the bike. If it all works, I'll probably bolt on a pair of the "bear-trap" type trial pegs to the mounts.
WIth the pillion pegs flipped and swapped, I had a good old bounce on the bike and they didn't move. I don't think they will unless I land hard enough to bottom everything out. Even if they do slip, it'll only be pivoting down a couple of inches, I'd need to stop and move them back again but nothing that's going to cause an accident.
I just got the brake lever sorted out. Looks a tad sketchy because I based it on cardboard templates and cut/machined it freehand but I'm pleased with the overall functionality and better, it bolts straight onto the original pivot.
Off the shelf clevis joint.
The bit of flat bar trapped under the locknut is to butt against the original "stop" so it doesn't over-rotate backwards.
All in place.