Thinking about this some more - I really don't think you want to go with the paracord.

Why consider paracord?
Simple - because it's light. Ropes are heavy - esp. if you have to carry them up hills for a long way. So people are always trying to reduce the weight of the rope.

Several responders here have pointed out that if you were to take a short bounce, the rappel rope would be subjected to a much bigger force. You might easily break the paracord, even if it is rated at 550 pounds. That's a very good point. And as I think about my old climbing days --- I gotta' say that it's very easy to bounce on a rappel rope. Happens commonly. In fact, it would be pretty hard to rappel without ever bouncing on the rope. Maybe if you did a direct vertical "free rappel" you might pull it off - if you were super careful.

There's another reason to reject the paracord. The strength of these cords and ropes depends partly on the outside sheath that's woven around the inner core of fibers. That outside sheath can supply as much as 30% of the strength of the rope. So if it gets damaged - your paracord would be a LOT weaker than you thought it was.

So if you start experimenting with crazy rappel hardware that might work on paracord, you could wind up seriously twisting or damaging the sheath on the cord. That would not be good.

I think what we've established is that regular paracord (of the size you have in mind) is just not a good idea.

What you need ... is for someone to invent a super-strength paracord that's specially intended for rappeling. If anyone does that, you could be back in business!

Pete