Here is my take on the external spool holder. It actually works surprisingly well. The full setup looks like this:
The print bed is a Fleks 3D 8 inch Delta bed held in place with magnets.
And here is Yoda as he came off the run:
This is how the spool is loaded. I just use a simple Dremil felt pad as an oiler.
Under the hood, here are the parts:
It is basically my already published ball bearing, which removes vertical friction:
Into that, I insert another printed ball bearing that reduces horizontal friction:
The resulting assembly looks remarkably (but unintentionally) like Leonardo's tank design:
The spool diameter is of course a removable piece:
I've had fantastic results with this. Probably some of the best prints yet came from this setup. Yoda was printed in just over one hour with no "dings", "warps" or adhesion errors.