Breakaway roping questions?

I am hoping to try breakaway roping sometime this year with my mare. She is a 11 year old half QH, quarter TB and quarter Arab and stands at 14.2 hands. She is well conditioned, has a nice topline (although I continually work on adding more muscle to the top of her neck), and is light on the bit. She responds to leg cues, bit cues, neck reins, and stops well and I will sometimes even ride her in only a neck rope. She is patterned in barrels and poles but is not yet finished as she has only been training in those disciplines for a year. Here is a picture of her, taken yesterday. It is not a perfect conformation shot, but it shows off some of her muscling http://tinypic.com/r/2ivle6s/5

Do you think she would make a good prospect? I have thrown a rope off of her, dragged things, taken her on countless trails and she is perfectly bombproof.

She is barefoot, and is doing great that way. She has hooves as hard as rocks and does trails over all sorts of ground. But would being barefoot mean that she could not rope well? She knows how to stop on her hind end but does not have sliders.

Also, can I do breakaway roping in a treeless barrel saddle? She is very hard to fit western, so I barrel race her in a Bob Marshall saddle. I know I can't attach the rope to the horn, but would simply doing breakaway affect the saddle and/or her back?

Lastly- would I need a tie down? I would prefer to not have one, as my horse prefers as little pressure as possible.

Thank you!