Well first look at all the good/bad things about the 4 big maps.
Fester:
Closer bases(in some cases too close)
Closer zone controls( no more zone bases controling airfields 4 sectors away)
Vh vs. Vh
Trinity:
Fair base distance
Nice use of mountains( sometimes a bit excessive)
Some mountain ranges act as too much of a barrier
Zone control thats 4 sectors away
Vehicle spawns that dont reciprocate
AkDesert
Good base distance
Good elevation changes( i know, some are a bit whacked, but at least they tried)
HQ elevated to make NOE hard
Vehicle spawns 3 sectors away
Big Isle:
Excellent carrier ops
Fields too far apart
So in conclusion i would make these points:
Make bases close enough to find action yet far enough to make covering them from another base a real factor
Airfields are for planes, Vbases are for gvs. Use the Vbase HUB design. Keep vhs at airfield for defense, not for attack.
If a base is on the coast and can be hit by cruiser guns, for gosh sakes, give it shore batteries to defend itself
Elevation makes for fun and nice scenery
Keep zone controls tight. Nobody like taking a base thats supplied by a zone base 4 sectors away
My last point might be somewhat niave as i am not a map designer myself. Is it possible to mix up terrains? I mean have some green rolling hills, some desert, maybe even some tundra all on the same map. Its not like we have to worry about weather and growing seasons in AH anyway.