i.e. rather than using a normal single base with figs on, those bases are 2 x 2 the normal FOG size (for all other than skirmishers & elephants which are twice as wide and just 1 base depth deep). The bases often have fewer figs on them but in a more scenic/modeling style, as figures are not crammed on the base as in normal ancient bases. It allows a much more scenic and artistic method of finishing the models/units - which appeals to the modelers in some of us at least.
For FoG-AM the base size and movement would stay the same and an 'extended size base' would represent the normal number of bases for FOG. So 4 normal bases in a 2 wide, 2 deep formation in most cases.
The only issues I see are:
* it obviously limits formations - but likely not too much in many cases,
* no columns of troops for the units/troops so based as they are deployed 2x2 - again that's the penalty you take for this type of basing,
* would require a method of marking destroyed bases, so that's a pain but not that major of an issue - we mark status already do an extra is not a major thing,
* if 2 bases are destroyed and the unit is still active it would be deeper on the table than it actually would be using normal bases - which may effect pursuits etc.
* adds some issues for troops turning to face if attacked from multiple sides - but actually it may make that bit of the rules easier as there is no option of turning some bases to face.

* would not work for all armies and units, but may for some/most.
Do you see other issues in this and would it work?