Thank you Ian for the reward! It's a fair trade. Thanks to others for hipping me about a common practice that may have its reasons;
I see that for many players my point may be moot; road-tested musicians seem to say that it's nothing insurmountable.
Dustin, my intent was sincere; I could have kept the joke, although I thought that was the original topic,
a six-string guitarist wanting a ten-string guitarist to tune down.
I mean if your point were true then how is it that 6 string guitars are made in various scales from 25.5" all the way down to 23" to be played in E?
Scaling is not only string length but tension and guage. Earnest points out:
I think you would really prefer thicker strings when you use a lower tuning.
Every instrument is designed with pitch in mind.
A steel guitar can't sound its best with slack strings, and one would definitely feel the difference in the bar.
I can't think of a situation where a player would want to sacrifice that, unless it was permanent or life-changing.
The only solution I can imagine is to have a D-10 with one neck tuned down.
My main concern, as with the red box, is looking at one key on the guitar as you play and hearing it in another.
The stability of the musician as an instrument is as important as the stability of guitar tuning.
My bass is my handy pitch reference. It's stable, it never gets tuned. I think the same thing for my ears,
having them be used to a G sounding like a G.
I can see why one would change keys for the vocalist. I imagine Meisner and Furay's voices, like Yoakam's,
age like mine and would need to be conserved.
Once, a cantor came to town to sing at the synagogue. I met him there so he could sing me the A he wanted,
several Hz flat. I guess that's the only way he could sing on key. Maybe it was for the resonance of his voice.
I broke an agraffe (heavy-duty string tree) detuning it. I'm sure it took a while to stabilize after retuning. Most likely it was left flat.
You hear a lot of irrelevant stories from piano tuners. I'll try to be more careful in future.

Thanks for your indulgence.
But it is for certain, the way to keep a piano or a bass in tune is to tune it as little as possible.
I realize that basses and pianos aren't steel guitars, just extreme examples of stringed instruments, following the same principles.
I mean, imagine a capo for a piano!