barrel ease of removal - hmm, never thought of that one. The middle ion on my setup has a cocker-threaded breach and it does take significant time/effort to remove the barrel in the field.
that being said, I rarely if ever have issues with the ions breaking paint.
I did learn a lot from your superion design - after watching your disassembly vid, i knew that I needed to make the ions bolt out back. I also felt like I needed to remote all the tanks, and that some kind of stock was in order. The trion wasn't finalized yet in that pic - heck, it's still not finalized now. It's a work in progress
as far as aiming the guns - I didn't bother trying to aim them in any specific direction other than straight forward, I figured that at the range I normally tag people with this thing, it simply wouldn't matter.