Re: Vectran sleeve for anchor rode?
I have been kicking around the idea of an all dyneema anchor line for a while. Sure you loose stretch, but so do all chain rodes as well and I don't see anyone screaming about all chain as a problem, though a snubber would be in order.
The biggest issue as you bring up is abrasion, but frankly the best thing for that would be a larger sleave of 12 strand dyneema added to the solid dyneema core. There are also some abrasion specific covers you could look at made from tightly woven Dacron you could look at as well.
As for a dyneema core over something else. I wouldn't. The same reason plastic tubing makes such a terrible abrasion sleave would apply. Ie the two lines stretch independently of each other creating a huge amount of internal friction.