Most of my favorites have already been mentioned. I fail to understand the draw of most modern cartridges in this platform, very high pressure cartridges are not as well adapted to break action, and frankly, there are many inexpensive bolts that are stronger and more accurate in general as well as now CHEAPER.
I have thought that the Idea of having various bore diameter barrels, and you order them with a particular chamber is a fabulous idea. It would NOT present a liability as you would have to order them from a menu that the factory knew was safe.
That being said, there are some that I would especially like to see, actually- "families" , that are based on the same case.
218 Bee/ 25/20 / 32/20
219 Zipper= 25/35 = 7x30 Waters = 30/30 = 32/40 =357 Herrett = 375 (38/55)
30/40 Krag, 405 Winchester, 40/70 Winchester.
Also, since barrel blanks are pretty long, why not offer them in 4 " increments for a reasonable charge? 16-20-24-28-32"? They have to be long enough to make a BC @ 32" to start with, and 26" for 25/06 & 280, so have a base price, plus chamber charge and cut & crown to one of the above lengths.