In my opinion, not a whole lot (my wife's opinion may differ slightly). Storage Vacuum bags will hold pretty much anything you need. These can be jammed into any available space.
More important priorities are;
1. Easy access to motors, chargers, pumps etc.
2. Food storage.
3. Booze storage.
To this end the outboard side of the hanging locker in the Aft cabin will become an electrical locker.
Air vents (and possibly a small fan) will be provided cooling and the item can be readily accessed for maintenance etc. Plenty of room is available for hanging clothes, should the need arise.