the idea of so much water is to allow some of the long range bombers their fun....with most of the other battles going on in a smaller more compact mainland area..below center. (a little give and take for both sides)
I happen to dig naval battles from time to time...and they are rare...so perhaps all that open water could call for more CV's.... I also like the idea of the upper tier of islands on top not having any air bases...just Vbases and Ports
agreed on the fact that the starting positions must be equal...
Starting positions dont need to be symetrical though, just "average equal". That's what I dislike about most of the current MA maps, but at the same time to creat equality without symetry is a bi... beast, so my hat is off to you if you undertake this. Key things would be number of bases and types (equal types, altitudes, distances from strats/HQ, vehicle spawns, etc.. ), distances from base to base, distances of front line base to opposing frontline bases (when the map first starts), aproaches/access to targets/areas (IE: britania has a bunch of 10k mountains around it's HQ/city area, an uneven disadvantage is if the island countries had their HQ/strats at sea level and within reach of an off-shore CV's guns), etc..
I love naval battles too. One thought comes to mind with all that open water, is that you could have a lot of ports and a lot of CVs maybe. If they were all operating in the middle oceans a good amount of time then I can see frequent fleet vs fleet encounters, but they'll be random, sporatic... and likely most of the time if two CVs coem within guns range on each other, no player might not be around ot even see it before tboth fleets extend away.
If there is a low number of CVs limit, or if you want to increase the frequency/likelyhood of this happening, then lowering the amount of open water, creating more narrow "channels" between bases/islands (similar to what I see in a lot of the current MA many-island maps), or basicaly anyhting that funnels the CV movements into particular areas, will increase the likelyhood of contact. I personaly like your open water idea more if you can get the map to support enough fleets for each side that they're bound to stumble into one another out there in all that water. Might be fun to see what it would spawn in the player base, maybe more anti-CV missions based off of carriers or coastal airbases.