It looked like the small rope you use to secure stuff to the deck is tied around one of the foot straps. Any reason why you wouldn't use something sturdier, like the A-frame?
The hiking straps are plenty sturdy (they're strong enough to hold your weight and a passenger as you hang your weight over the side of the boat) and I wanted something that would keep things in the centre of the boat. Tying anything off of the A-frame down low would mean that whatever is tied off could drag in the water when you fly a hull. This location is also out of the way of anything related to sailing, like the rotating mast, furling line, sail etc, and even when flying a hull, or tipping, if you tie things correctly, the furthest they'll go is up on the outer hull, instead of into the water.
Is there enough clearance between the water and the underside of the deck to (somehow) fasten a paddle or anchor under there?
I wouldn't fasten anything on the underside of the boat. A large wave, or even a pitchpole (which on the Bravo, isn't a cartwheel type of tip, it's just the front end burying itself into the water causing the boat to rapidly slow down) could cause you to lose whatever is there. Plus there is no way to inspect it while you're sailing.
I used to think about taking a paddle but now I never do. It greatly depends on where you sail, but Canadian law only requires that you have a "manual propulsion device" which can include moving the rudder back and forth like the rear fin of a fish. The Bravo will move in almost NO wind, once you get used to sailing it, and if there is actually no wind, rocking the rudder back and forth can usually move you as far as you need to go. Sometimes I raise the rudder partway so that it gives me a longer sweep in the water.
Obviously that won't work in a high current area, but for all of my sailing, I have yet to find a need for a paddle on this boat.
I do know that some people take a kayak paddle, take it apart, and then strap one end to each side of the A-Frame. Here is a picture of someone who put both paddles on one side.