Here's an older pic on my modified cougar, which is going to be similar to any saddle that uses a rigging plate. Basically the roll n lock is literally zip tied to the back, so that no matter what, there is really no load on it, it simply acts like a movable stopper knot, which of course is backed up by actual stopper knots. In practice, it works swimmingly. Of course, this is against all manufacturer recommendations of use, e.t.c, e.t.c. Richard Mumford, the guy who invented this use, even went so far as to actually do break tests, which i personally chose to be good enough for me.
B, once again you aren't wrong. It is further complexity, which unless serves a very exact and worthwhile purpose is useless and gets in your way. However for me personally, after having it, i would forgo many other things before losing it, mainly because my ropewalker setup is based on it and i won't ever go back to not having that lol.
It solves both problems common with an actual hands free setup: 1) what to do with the climbing system because your chest box needs to be in the same spot and 2) what is your actual tie in, because if you do a rope walker setup only using ascenders you need to use 2 because they aren't rated for life support. By using the extendable bridge, my rrp (or other climbing system) simply goes above the chest box, giving me a bomber tie in that i can even rappel from, and i simply walk. Not for most, but works very well for me.