Have you thought of a tropical weight dry suit? I've never used one but a regular guest at the resort I used to manage swore by them and always used one in the Lembeh Straits where it was 29 degrees usually. He said he could stay as warm as toast both above and below the surface and didn't suffer overheating problems when on the boat.
I know Bermuda well and can certainly appreciate the issue - and then there is the massive water temperature variation between summer and winter. A summer weight wetsuit for the summer and a good jumpsuit underneath in winter might work well.