I personally do not feel comfortable leaving any dog on anything chewable unsupervised. So hell no I would not recommend moutain rope.
I would recommend a sturdy cable set-up or a proper chain set-up.
Mine have cable tie-outs at my moms... the cables are a couple years old and already need replaced from being worn by the active sled dog mutt girls. I have a couple sturdy chains I had made for camping that I will probably replace the cables with. One cable I bought at D&B... its a good thing Scout is a good girl because its a cheap P.O.S. The other was given to my parent's by the people who acted as brokers and helped them pick out their BC, I have no idea where they got it, but its sturdier. Which is good because Lily is a nut on her tie-out, typical sled dog theatrics lol.
I'll be honest, I don't 100% trust the cable either. Both of them could chomp right through it if they really wanted to. They are a little more hardcore than the average pet dog though.
Make sure the dog is wearing a properly fitted, very sturdy collar as well. No break aways (plastic, nickle, brass, hybrid.... doesn't matter what kind of snap it is DON'T use a breakaway, especially if the dog will be unsupervised!), martingales, no buckle slides, etc. I have used Lily's "For Ella" on her tie-out and it is more than adequate, however its not recommended for that use!
The only collars I truly trust for tie-out are Shane's at Stillwater:
Stillwater Kennel Supply --
I use the 1.5" 4ply show collars. I put an extra O-ring on Lily's purple and yellow to help slow the wear on the collar since the colored nylon is softer than the black. In fact they are the only collars I trust 100% not to fail on Scout period.