No longer need 16' speaker cable pair- options?

If you like the cable, I would leave it alone and route the excess cable appropriately.  It's not that much excess.  IMO, a reterminated 6' pair of cables would not have much value, especially if you deduct the cost of retermination.  If you needed a 6" pair for another system, that's a different story.  

I don’t exactly need a 6’ pair for a 2nd system right now but it might well come in handy in the not too distant future. The cost of re-termination is about 40% of what a new 6’ pair would run- 

Its doubtful you will hear any improvement from the shorter length. So the question is how much is the better looking shorter length worth it to you? Some place like the Cable Co will probably take your longer cable on trade and sell you the shorter one for next to nothing net. The other way, re-terminate, you spend a couple hundred to get to the same place but with an extra 6 ft cable worth maybe... a couple hundred. That's if you can sell the shorter cable. 

The only way I see it worth re-terminating is Option Four: have them cut the 6 ft wires, don't terminate, and use them to replace some of the internal speaker wires. Probably not something you'll be into, especially with those hard to work on speakers. But I've done this before and its almost guaranteed to be a bigger improvement than any of your other options.

Leave it alone.  Nothing to be gained, and who knows, some time in the future you might need longer ones again.

+1 twoleftears, a nice coil looks good, and some risers doesn't hurt a thing, adds an artistic flare to the look.... Culture.... Yes... Cable Art...

The NEW thing of the future "Cable Art by so and so!!!" yup!!!

Regards