i still have the omd5 in a nauticam housing, but think about going back to aps-c.
Could be a sony 6300, for weight and size, or the nikon d500, for that i have all the lenses i need.
A7mkII is nice, but the housings are too heavy...
The reason is only the low light theme....
I thought the Sony 6300 was roughly the same size as the A7 with the main difference being full frame vs aps-c ?