Good innovative thinking. You have to throw a bunch of ideas against the wall before you find something that's more practical then all the other climb tested ideas in current use. It's a worthy cause.

A potential advantage is the reduction of carabiners used in the system. To further optimize and reduce bulk you could thread the rope and lock it just using two holes on the Paw since it's a closed system anyway (with the bridge tied off with the Blakes). That way you'll have two more holes available to repitch up using the other end of the rope.

One concern with attaching rope directly to the Paw is it looks like you're putting a sharp bend in the rope where it carries the most load from the "up" rope. With the straight vertical termination plate the rope isn't bent as hard.

One note about your slack tender, you may have already figured this out... if you attach it with a slip knot and clevis on the up rope (instead of the bridge) you can move it higher and closer to your Blakes to reduce slop in the system when you advance the hitch.
-moss

i too was concerned about the sharp bend, but it is'nt an issue to me...i have a arborist biner for work that you tie a rope end to...and it makes the rope have a much sharper and tighter bend. When i contacted the manufacture, they stated that the sharp bend was'nt and issue, and that ropes had been tested under load and dropped tested with zero effect at the bend.