I'll chime in with a global change to army lists that does not require reprinting 13 books.
Figured that I would note some thoughts on army lists posted in this thread
viewtopic.php?t=20744
Charge AP per BG instead of per base. Add discounts to bases over certain threshholds to reflect their diminished marginal utility.
For instance, the 5th and 6th bases of a mounted BG could be half-price.
MF/LF could cost the same AP in 4-packs and 6-packs (probably 5x base AP price).
The discounts could differ between Drilled and Undrilled, as the latter face greater downsides in larger BGs.
Supporting LF/MF in mixed BGs could be reduced in cost -- LF/Av/Bw in a mixed BG are not the same value as stand-alone BGs. So charge 3 AP for LF/Av/Bw in mixed BGs, but 5 AP standing alone.
Rethinking how troops are priced would bring army construction into line with game play. Namely, the game is played, won and lost at the BG level. Buying troops as bases to use them in BGs exacerbates the differences in quality found at the BG level. Small BGs are often too cost-advantaged (4-packs of drilled MF), while larger BGs tend to suck primarily because they are large (6-packs of mounted). Having more stands provides some value, but virtually no BG value equals the sum of its parts.
Changing the AP focus also frees up some wiggle room for any number of debates on game balance. The agony over balancing undrilled vs drilled could be made easier if there were two levels of points adjustment. The current base price difference AND a second level of price changes at BG margins. So the authors could balance 4-packs of MF (drill/undrilled) with the base price gap, but account for other differences with BG pricing -- give undrilled MF a discount in BGs of 8-10.
Furthermore, BG pricing could restore some historical distinctions that existed in DBM but have not imported into FoG. For example, Knights in FoG are Manichean. Bring HvyArm/Superior or nothing. Gone are the finer balances of Kn(S/O/I). In DBM, Kn(S) were obviously the best, but Kn(O) and even Kn(I) were not hopeless given their points values. Presently, almost every army with DBM Kn of any flavor has "proper Knights" as a line item, including German (Kn(I)), certain English (Kn(O), Komnenan Franks (Kn(O)), etc. If we priced troops as BGs, FoG could recapture some of the historic interactions between Western knights -- e.g., French/Teutonics > Spanish > German -- by maintaining the "proper knight" base, but increasing minimums for Germans/Spanish to cheaper 6-packs. They would be powerful in combat, but more cumbersome to use relative to French/Teutonics. If you implemented such a list change under the current system, German/Spanish Kn would disappear, because 138 AP for a Kn BG is impossible. If that BG cost 115 AP (5 x base), that might be worthwhile.
Although the price changes could be dramatic, it would not require an overhaul of all the army books. Instead, you could insert one page in the rulebook (and use errata for the intro to each army book) to change how armies are built. None of the detailed lists would need revision, though once the system took root, you could build some nice distinctions with army list errata and/or new books.
tl;dr = restructure AP costs at the BG level instead of the base level. Some larger BGs become cheaper per base.