Hi Mike, I hope you are well.
I am assuming you are thinking about some sort of Weissenborn type instrument. They are very cool and you could soon hit big money if you are not careful. I am sure you will try before you buy. Very important for any instrument but I think especially so for these. I have a couple of these and they are definitely not for sale, but I can give you my thoughts on what I think are the pros and cons of this type of instrument. First of all they are great fun and can sound epic. They are very easy to get pickups fitted and take effects very well if that is your thing. But the big thing about the sound of a Weissenborn is not the mid range which is very good....... It is the bottom end. They are magnificent in the low register, even tuning way down to C. So low bass tunings and D tuning are in the weissenborns element.
Now I did try C6 many years ago on a Weissenborn and I soon changed back. It was not that it did not sound and play OK it was just that these guitars sound so much better with a low tuning on the bottom end. Although I am sure you will get it to work. I just think you will be missing a main character of the instrument. As I am sure you are aware you need to be careful about string tension on a weissenborn. Especially the more expensive luthier made or vintage instruments. If it is possible to borrow one and try a set of C6 strings you can obviously make your own mind up.
If it is ragtime and C6 tuning then for me a better solution would be a spider bridge resonator. I am sure you have had some experience with these but they do sound great in the C6 range. I am not a Bluegrass player but do play quite a lot of Hawaiian type music with a bullet type bar and it works very well for me.
Here are a couple of Weissenborn videos of mine. One in D tuning.... the other G tuning with a ow E.
https://www.youtube.com/watch?v=RF8gxxbJxtI
https://www.youtube.com/watch?v=AfNjhM9MPbk
You can hear just how great the bottom end is on the D tuned instrument.
I wish you all the best in your search for an acoustic instrument and if you have any questions I will only be too grateful to help.
All the best,
Mike