I guess Id have to agree with Flux...
some "engineer types" I've met get really bothered by pipe over pipe.
But its never going to sieze... it's probably never going to wear out (if it does itll take a LONG time)
and it provides nice resistance to yawing which is nice... very fast yaws are hard on things, I think a bit of stiffness in the yaw bearing provides some stability. It may also be of advantage when we have the "dangling" wire down the tower, to help prevent it from twisting up too fast. pipe over pipe works great
I wouldnt complicate things.
But if you like to complicate things and want to spend the xtra money and all - I suspect a wheel spindle would work fine. Of course, youd almost have to use a tight bearing if you chose to incoorporate slip rings...
My bet, is any bearing you choose though will fail before pipe over pipe fails.