Bi-wiring with unterminated speaker wire?

Why not but the wire itself and how it's configured  (twisted etc) can have an effect on the sound. As any wire will.

Yes, you can!

Yes, and I’ve often wondered if bare wire is a better and more pure connection versus introducing more connections and different metals by adding spades and plugs — not to mention the added expense of doing so.  Go for it!

HI Soix- you can stop wondering.  Bare Wire connections ARE the best performing for a wide number of reasons.  Here's the catch- bare wire is the best connection possible for a VERY short period of time.  Unless the bare wire connection is treated and/or sealed, it will very quickly start oxidizing and the performance will suffer.  That is the main reason for formal terminations- you can seal the connection and dramatically slow down the oxidation effect ( notice I did not say eliminate it).