I've never had one break, but ride enough that it's possible it'll happen at some point. I've heard that the early five speeds (74-5) had to large of a boss and the spring would bind. But our R65s are newer and out of that range.
I was thinking like this:
Use a bolt with a welded-on arm instead of a drilled oil fill plug. Drill a hole through the bolt and either mount a seal or a felt inside to keep the oil in.
Bend up the steel as shown inside the transmission. But once it passes through the bolt, bend at right angles.
Attach a spring to keep it disingaged.
Attach a cable from the bolt's arm to the rod, then to the clutch arm at the back of the transmission. Make it easy to attach, and then when the clutch is pulled in, it also releases the 'pall activator'.
That way you'd be able to shift normally.
That's an interesting idea to put a hole in the back cover. I even thought of running a cable or rod up through the top of the transmission. But it seems like the simplest solution is to do what I've just laid out. It would still be small enough to take up very little room, and could allow the bike to be ridden many thousands of miles normally until the right time to fix it properly, and would eliminate the need to slip the clutch through towns or run down the highway in third.
Even though I've fixed something like ten or twenty of these transmissions, I don't totally understand them. Thinking on this more, it seems the pall needs to be in contact with the pins all the time and has a spring because the shifter moves back and forth. It may be possible that a spring type mechanism is all that's needed on the outside of the transmission (with our rod solution) to provide constant tension on the pall arm. That would be a much easier solution!
