Multiplayer/solo battles are set up differently and other set of circumstances apply there – thus you are indeed able to select all factions in Redux on VI/V.2.01 but not while running upon V.1.1 versions of redux. Unlocking factions in the way you describe is not possible in MTW due to hardcoding (still, all factions can be unlocked in other ways, by modding).
As for redux seemingly have “too few” available factions to play… I’ll be happy to have that discussion once you (or anybody else) have played thru some 15-20 proper redux-campaigns, preferably at least twice with each faction available by the default design. Then any such discussion would be meaningful to some degree. At this point you simply don’t have had a sporting chance to gather enough "redux-experience" to realize that redux and MTW is hardly the same thing or even similar in how they internally function as games. While your (intended?) references to raw MTW (and work based on that perhaps) are understandable – I would hardly consider it as advisable or practical as far as redux goes.
There is little doubt that redux due to design offers more diversity and thus a more challenging and demanding game in general, while raw MTW offers another kind of game with more structural conformity by design, which in turn allows standardized solutions to be more viable and efficient. I know this
because I have played raw MTW for at least 3-4 years straight
before I ever started to work on MTW-redux. I know both well enough to be able to see and identify most distinctions between the two – personally I think that this is a necessary prerequisite in order to successfully discuss them in a combined context somehow.
Redux is more or less a new game – which by all means offer familiar settings, same kind of elements, activities and components but internally there are few similarities to be found; models, mechanics and variables are with little exception created from scratch, usually ignoring the previous CA-design, as the new stuff were created on the drawing-table. Redux is literally designed “outside the box” and it does not attempt try to hide that either. Factions and the number of factions, how these are designed, including playable ones, and the overall approach to that are no exceptions to that rule. Nor should it be...
Anything else, fire away people...
- Cheers