I quite agree, The chassis like the AS wiring is very poor, or should I say not up to modern day standards. I have rewired all the domestic 12volt system because of undersized wires. For example when the lights were on, and the pump comes on the lights go dull. So I have replaced all main power supplies to the fuse boxes with larger size cables. That has made a wealth of difference. In fact I re-cabled all the house batteries - see photo.
I removed the chassis battery to the space between the bulkhead under the drivers seat and the slide out compartment. Slung underneath it fits beautifully, and as the battery is of the "none maintenance" type it is just the job. This left just (Only Just!) enough room to fit the four 6volt 125 Amp/Hr Batteries in the battery tray under the step.
The chassis fuse box and holders I think is very poor, including access to it. I find it difficult, being a bit portly, to squeeze under the dash to reach the connections and fuses.
I have now started to rewire all "spare" and "axillary" connections that are using the spade inserts into the fuse box, from a single source from either the chassis battery or house batteries depending on use. In each case I have gone back to the main supply cable, created a soft fuse block and taken wires from that to the likes of lights, heater, dash lights, horn entertainments etc.,
Each of these circuits now has its own fuse rather than relying on one fuse of the P30 block to cope with many items. This way when a fuse pops, not everything stops!
I will photo all when finished and set it out on a wiring diagram in AutoCAD. When all thats done I will post it for any one to take off, but as my "free time" is limited it may take a while.