PineSapKnuckle

Hehe, I think we agree!

Yes - sort of. The way you use fishermans as a termination knot. Not a stopper knot behind the shackle, but pass the rope through the shackle and tie it back to itself. You would have the adjustability as in your example treemotion, although it is going to be little laborious to untie and move the knots.

..on the other hand if splicing will not work, you can just use double fishermans on both ends of the bridge if the knots do not bother you.

Good idea, splicing your own custom bridge! You get to choose material and dimensions... Conventional splicing limitations might be problem at least with very short bridge.. Burying the splice tail takes some room.

Tree Austria 3.1 harness has replaceable bridge: http://www.drayer.de/shop/en/Arbeitsgurte/Harnesses/Arborist-harness-TreeAustria-31.html You can get various lengths and replace it yourself, you just have to glue the shackle bolts back: http://www.drayer.de/shop/en/Arbeitsgurte/Harnesses-accessories/Central-bridge-TreeAustria-31.html I cannot find mention of the CE-approval though.