Sounds like a lot are onto the right idea.
Short story - years ago when these plastic, steel and aluminium overcladding cladding systems first came around there were a lot of people jumped to spruce up older houses. Many were under war service home loans (talking 70's, 80's, etc). Part of my Dad's work was as a war service building inspector and insurance assessor. After the work was done people often asked to have their homes reassessed for insurance purpose, etc. Dad would turn up, devalue the house and write down the insured value - and not just a little! Many people were not happy after having just paid a packet to "improve" their house to find it was noticeably devalued. The reasons were simple - the cavity between claddings provide a perfect spot for vermin, decay and corrosion to occur and prevented clear inspection of the actual status of the structure.
In short I would recommend steering clear of the overcladding option.
Have a look at these products after a good hail storm - not pretty. If I recall I don't think war service would insure them for the cladding replacement either just to add further injury.
Deseng.