Cobra, Goodwood, Totalize, Gazala, Supercharge, El Al, Alam Halfa, Mersa Matruh, Siege of Tobruk, Aberdeen, these are all IMO big enough to support 64+ players with the current flag placement & assets available.
FoT would probably be epic as well with increased playercount. Sidi Rezegh, Lebisey & Falaise are question marks.
St. Lo plus the infantry maps (Giara, Tunis, Bardia, PdH, PHL, Anctoville, Brest, Ramelle) are quite small and/or have few assets to support moar players, but seeing a total carnage every once in a while (in the style of 16/32 mapsizes in FHGN's) would be lolsome.
In the end, the increase in FH2 playercount would make the game more infantry-heavy and thus more WW2-like.