Wow ... huh?
There are more than a few reasons, besides 'convention' or typical installs, for standard wiring practices, think USCG, ABYC, BIA standards and such. While the voltage per side of the circuit is the same, you'll be leaving your systems energized for potential by leaving them connected 'hot' on the + side.
I'd run a main helm of 8 AWG or suitable ampacity (for your load) up to the helm. Attached is a simple VSD drawing of my current setup ... to me, it doesn't get any easier than that. Then loads at the helm only need the wire size for their amp load and length of the circuit (and remember 'length' of the circuit counts the TOTAL run to and fro from the device, so a load 3' away needs to be calculated for its amp draw being 6' of circuit length, as that is the premise for how all ampacity/minimum wire gauge recommendation tables work).
I fear - by your method - that you'd need heavier AWG than practical, on each ground circuit. by keeping all connections going back & forth to the console. Now I'm no electrical engineer, but by killing the ground you stopped the loop, but the connection + will still be live to the device, so you could ruin devices by putting them in or out of the circuit by working on a live wire.
The standard practice is also to put the circuit protection on the + positive wire in negative-grounded 12 VDC schemes. Anytime you or anyone else needs to touch that circuit/wire - remove the fuse or trip the breaker - and done deal, that circuit is now no longer energized and can be easily serviced. So I have to ask ... why would you want to do what you propose :roll: ? God forbid it causes a fire and you won't have any insurance coverage and I'd say you had liability even after you sell the boat.
Even if technically 'OK' ... I also believe, that if nothing else but for resale value purposes ... that I'd walk away FAST from such a wired boat. But hey, it's your $$ ...