Fair enough. Since my start in miniature gaming was with 25mm Napoleonics, I'm sort of stuck in that mental mode by default. (And I've painted a full French corps and then some in 25mm.) You do make a good point that 15mm or smaller makes more sense for the "big battalions". The Battle of Austerlitz would look better (and might even fit on a tabletop) at 10mm. [Although painting Napoleonic uniforms at that scale ... YARGH!]
As for a mass battle game by Wyrd, let me clarify. I like Malifaux as a small scale, small monetary outlay skirmish game. Turning it into a mass battle game would warp it into something else and it would no longer have the "feel" that makes the game attractive.
Now if Wyrd's venture into plastic proves successful, perhaps they could develop a mass combat game in a different genre or universe, one where big battles are the norm as opposed to small skirmishes. Heck, perhaps something that interlocks and so you could play at different scales. For example, using a hypothetical sci-fi universe using 10mm figures and vehicles. The first rulebook would be at the company level, so the basic movement stand would be the platoon. Emphasis is on small unit tactics. Next step up, Brigade or Divisional level with emphasis is on grand tactics. Finally, the army corps level. Ideally one uses the same figures and vehicles on the same stands for each game; it is the level of detail that would change for each ruleset. At the company level, weapons and vehicles would be detailed, with individual stats, thus a Type A medium tank moves faster but has shorter range than a Type B medium tank. At the opposite extreme the corps level, those details are abstracted, putting the focus on maneuver and morale. Small technical details get lost in the wash at that scale.