That's extremely crafty Geoff, alot of thought went into it.
I have a half cabin and what i've done is as followed. In front of the u-bed as you walk into the cabin (where you stand and steer), from one side of the boat to the other i've built hard wood storage. One half (or just over) of it is lowered to allow for easy access to the cabin, it's used for life-jacket storage, plus it's a good level to sit on while fishing. The other half i've raised about 50cm and installes a 20L plastic box live bait tank. Drilled a hole underneath where i've connected a hose to drain it and ran the hose out through the side and down to the back of the boat. As it sits high, drainage is no problem as the water is running on a down hill slope. The water input runs from the back of the boat (Bilge pump) with a two way on off switch for either a deck wash or the live bait tank. I've connected a hose from near the top of the bait tank drilled a hole in the side of the boat and ran it out the side to stop the Live bait tank from over flowing keeping the water running constantly. I have also installed a detachable metal basket that hooks inside the live bait tank to put other baits such as prawns, squid etc, keeping them out of the sun. This gives me alot more storage, which we all know is priceless in a boat, extra sitting room and good bait options. Will post photo's tonight.
Cheers,
Mark