i'm surprised you are taking this boat the direction you are. for me, boat-systems-use should be in concert. i thought the atlantic 57 was an updated stretch version of the atlantic 55 -- a 25K pound cat suitable for blue water cruising and manageable by a short-handed crew (think owner). for me, that "spells" keep things light and simple... while ensuring critical needs are met. i'd contrast that with another very high performance bluewater boat, the gunboat 66. while only a few feet longer than yours, this boat has enormous volume, and hence can carry quite a load. it is also a boat that is designed to be run by cap't & crew, with owners or guests "popping" in for vacation
. for this boat and this use, despite the light weight, popping on air con and other systems is the "norm".
all this stuff adds up weight-wise, and it all adds so materially to the complexity. now that you've added aircon, you're working on ensuring you can run it in europe
. you can get a great transformer for about 100 lbs. then you get to throw in wire, cords, connectors, mounting brackets, etc, etc. bit of a snowball to me... one of the biggest positive surprises for us on our cat, is the simple luxury of living almost exclusively off solar panels
. if you avoid the big draw AC stuff, you can achieve this easily... and not want for creature comforts. i'd still recommend a dozen "hella fans" for 'air con'. for the odd time you're at the dock and the sun is low in the sky, add a small lightweight multi-system battery charger (mastervolt or dolphin make 'em that will run from 90-270 volts and 45-65 hertz). you can pick up a light extension cord at home depot that will suffice for shorepower cord... along with about 7 adapter plugs for the various countries you'll visit.
an irony for me, is that you're taking your 'heater system' -- in my opinion a critical system for liveaboard
use -- in exactly the opposite direction ==> choosing forced air because its simple, inexpensive, and lower power. but you should consider mike's (of yogao) advise. hydronic heating is considerably more robust. it requires more power than forced air... but a unit that would heat your boat draws about 150 watts while running, and it doesn't run continuously. a 150 watt (occasional) draw doesn't even belong in the same thread as an 'air con' decision.
sounds like a great boat. good sailing!