Hi All
Well I didn't have a lot of time (so sorry it's very basic)
So here we go ... this is the original design (Which I really liked, [Looks easy to cut and the material can be maneuvered easily ])
On the other side of the arm is a plate the will move straight up and down, rods added to keep it straight (which you probably guessed)
The main idea is this plate is fixed and additional "plates" can be added/bolted to it, one example (and requirement) a "punch plate" will be bolted to this plate, allowing easy "swap-ability"
The bench underneath hasn't been fully thought through :) but the idea is it could be adjusted up and down to allow for different attachments
Well as I said this is a work in progress if you can use it, improve it, go for your life its open source... go nuts
Enjoy