Motorhomes with aluminium outer skin?

Yes both Newell and Prevost are aluminum skinned. Thanks Ernie...

Newell Coaches are aluminum skinned I believe.

my coach is a 97
the front and rear caps are fiberglass, whereas, the rest is steel

Showhauler uses aluminum skin

Aluminum and fiberglas are about the same when it comes to repairing. There are honeycomb fiberglas parts that are very strong and quite stiff. I worked on Raadomes and they were honeycomb. You took a pair of big pliars and pulled the dead Gooney Bird out, took a router and routed all the damage and then put in honeycomb and coverd it with fiberglas cloth, 3 coats of resin, 3 coats of filler and 3 coats of primer and 3 coats of paint. Very expensive repair and took a week to do it all.

Take a look at Holiday Rambler Admiral, Endeavor and Presidential. I have an all aluminum HR 5'ver and am very impressed. I think those Class A's are what you're looking for.

Steel... I didn't know that Ernie! How does that hold up and what year is your coach?

my coach has steel
unfortunately Wanderlodge is not in business

Some of the older Monaco coaches had aluminum skin, which included their Holiday Rambler line. Many of the fiberglass coaches have had delamintation problems. I am not sure that a fiberglass sidewall is any cheaper to repair than an aluminum sidewall if you have severe damage.
Even the Monaco brands with the aluminum sidewalls had a fiberglass front and rear cap. Aluminum/stainless steel front and rear skins might be limited to just the Prevost chassis.

Had a MCI and found the cost of maintaining aluminum skin, had a case where a UPS delivery van slid across the frobt of the bus, cost $26,000 to have repaired due to massive labor replavibg the structure in dash, front end, big job, bucking rivets etc.
Today have the Foretravel, fiberglass easy repair.
Dave M