Reb,
So far as the "re-design" of the receiver for thr Big-Bore series, that is a very simple-to-do re-contour of the exterior of the receiver which is much simpler than changing the basic interior dynamics of the action. Likewise, the Angle Eject change was relatively simple and since it applied to the entire line would have been economically cost effective.
I am aware of the use of the .358 case. If memory serves, this was referred to as the .356 Rimless. It was also done in a Marlin 336. If you are willing to make compromises in function to use a more readily available case, that is your prerogative. Yes, you can, usually by some degree of jiggling be able to use either the .308 or .358 case in a '94, but, the factories need to ba able to realize 100% functioning with standard parts. Since they are guaranteeing the operation of all guns they produce, it could be very expensive to them to make repairs to a large per-centage of their production because 95% of their clientele are not inclined to tolerate less.
Remember, reloaders and people who shoot frequently as do most, if not all, who read this forum, are a relatively small part of the sporting firearms purchasing public. These people don't, and won't tolerate a gun which does not function 100% of the time or needs to be treated in a special way. They will drive the compny or warrantee stations crazy until they are satisfied.
In short, and as I believe I said before, yes, in can be done. Yes, the action could be re-designed to allow this. No, it would not be economically feasible for Winchester to have done it. For Winchester, and all manufacturers of all products, manufacturing a product strictly depends on the ability to make it a paying proposition for the man mufacturer. No matter what we are talking about, if a company cannot make a profit, or initially believe it can, no product will be manufactured merely because a few people say they want it!