This was designed

... inspired by Franklin :)

A variation of my 'ladders within ladders', or, as he called it (and kindly explained in a much more intelligible manner than I ever could), my "summer swing ladder", a bit less strenuous as for the work-rest-ratio.

EDIT:
Of course I'm not reinventing the wheel here (or anywhere), it all goes back to the same concept as in Tracy's progressive ladders - what I was trying to do was to set it up (scale it down) rep- and rest-wise so that a (for me) really heavy weight gets manageable for longer sets.

rep ladder:
two hand swing (=transfer) - 1 swing L - two hand swing - 1 swing R -
two hand swing - 2 swings L - two hand swing - 2 swings R -
two hand swing - 3 swings L - two hand swing - 3 swings R -
two hand swing - 4 swings L - two hand swing - 4 swings R -
two hand swing - 5 swings L - two hand swing - 5 swings R
= 1 set, 40 swings (15L, 15R, 10 two hand), 1min

This rep ladder design can be easily adjusted to your grip endurance: if you prefer to have more two hand swings, you can simply stick to the original ladder scheme and do 4 rungs instead of 5, that's also 40 swings/set, 10L+10R+20 two hand, or you can also do both downhill.

The weight ladder, as I originally planned, would have then been:
1 set @ 16kg
1 set @ 20kg
1 set @ 24kg
1min on, 1min off, 6min/ladder

But Franklin's idea of doing it all @24kg was stronger... Oh yes, those blogospheric bees in our bonnets ;)

So I instead did 15 rounds @24kg
8 sets as described uphill,
3 sets downhill,
and the rest with 4 rungs and more two hand swings uphill:
1 two hand swing - 1 swing L - 1 two hand swing - 1 swing R -
2 two hand swings - 2 swings L - 2 two hand swings - 2 swings R -
3 two hand swings - 3 swings L - 3 two hand swings - 3 swings R -
4 two hand swings - 4 swings L - 4 two hand swings - 4 swings R

Total: 30min, 600 swings