.45-90 express is a simple, obvious winner since it can easily feed and shoot .45-70. I've got a Browning 1886 I had reamed out and use it as a dangerous game gun. It's quite capable on anything from deer to stopping elephants as long as the range is kept reasonable. The only problem is that load data is poor and the powders represented are often not the best options. I've had to do my own strain gauge testing on loads to ensure safety.
.50-110 express has the problem that there's no smaller popular interchangeable cartridge (unless you can shoot .50 Alaskan - there's a lot of similar dimensions due to shared lineage?!?), which makes it a lot bigger deal that the load data is junk. It's hypothetically quite capable though if someone worked up loads. Lots of .510 bullets out there, and Starline brass. I think it's one of those things you could get going, but would have to introduce both ammo and guns at the same time, which frankly I doubt Winchester is up to.
.40-82 seems like it's too far gone to resurrect. Not much in the way of jacketed bullets (Hawk?), and Jamison the only brass source. .38-70 I have to profess total ignorance of. I've seen references to a .38-72 - not sure if that's the same thing but I don't think so.
I think it would be easier to catch on new cases that were either .45-90 or .50-110 necked down to accept common flat nose big bore calibers. .475 Turnbull is an example of this approach.
Personally, I like this sort of gun. My .45-90 is probably my favorite hunting rifle, even though it only rarely makes it out of the cabinet.
