Fredy,
Almost the entire back half of our book is dedicated to small niche marketing, we even put our templates in so people can utilize what we have learned.With out giving away the farm-
1) How best to overcome the distribution ceiling? (e.g. hook up with major distributors along highways; set up a cooperative that engages independent trucking for several farms' harvests)
We did some work with a local CSA and restaurant (if you can find one you can work with!) Winter time was slow for us,our indoor production was mainly for special order Thanksgiving, Christmas meals. We always kept some grow kits also. Reishi was another we had a demand for much like chagga. Shelf life is great!
2) What mushrooms besides the staple oysters and shiitake (and maybe winecap) get and hold people's interest, and what value-added products can you make from them (including foods for immediate consumption...saw a lot of that and it would be great for a stand by the highway).
Hercium was a big one for along with piopinno, though your climate is probably not conducive outdoors. We also did a variety of oysters too, Golden, Pink, Italian, blue etc. to keep it eyecatching! We also dehydrated and made gravy amenders, rubs, etc.
3) What mushroom holds its value best when dried?
Shiitake, Reishi were some of our best dried, Morels chantarelles-black are some of the wild ones that do well also.
As I stated in the opening we have over 60 pages dedicated to the marketing aspects of small niche (mushroom) business www.mycelialmayhem.com heck order one I'll even signit for you

Hope some of this help. In closing I try to encourage to a) start small b) figure out your successful species for your area c) don't go hog wild and find your market area won't buy your product,there is a whole nameko story tied to that lesson learned! Still love growing and eating them though.
Dave