Heated Suits ????
From someone who managed to set their mountain bike on fire with lighting equipment not sure I will be trying an electrically heated wet suit.(Will it make tea aswell ?)
Batteries ; heating elements; neopreme and salt water dont sound a good mix to me !!
Resultant burns would take some explaining; (like my insurance claim for spontaneous combusting mountain bike).
On a serious note; problem isnt producing the heat (your thighs will produce 5 times more than 2 lithium batteries ever could) problem is keeping the heat in and at right places !
How many times have you sailed with a warm torso (your own that is) but freezing fingers/toes ??
Dont think my chest;shoulders etc are ever cold; its the extremities, which heated suits will not help. (Heated diving suits circulate hot water everywhere)
(Yes I know keeping torso/kidneys warm helps everywhere; but heat loss from that bit of hot suit will be incredble.)