There are of course many, probably all in fact, who in the perfect world would have liked even the map to be 1 : 1 in scale. However if the development team say that the resultant need to fill all that space means there would be way too many figures on the map for the target system spec to cope with I am sure your right. Waterloo will still be fantastically, scarily realistic.
However in order to totally defuse the issue, quite a few of your customers are very nerdish in pursuit of their military history hobby including me

Then for the huge battles, go with the scaling as shipped.
Am a huge fan of the system. Did years ago play around with the data files in ACV version. People could build maps scaled 1 : 1 with the size of the buildings, figures, maybe tweak the data files for range. Haven’t thought it all through.
But tweaking any editor, when it comes, so as to make true 1 : 1 in map size also easily playable, if people wish, would satisfy a curiosity in many and issue for some. No doubt anything other than a very small battle would not run on most systems.
I often state that the only wargames I rate as worth playing are Combat Mission, Command Ops and Scourge of War. Now also Flashpoint Campaigns and Desert War. Always hoped you would go Napoleonic.. from a tactics point of view even more interesting than ACW.
Looking forward to release,
All the best,
Kip.