Darren:
A 1/24 Beech 17 would be awesome.
On the matter of the Twin Otter, You may still be able to get your hands on the old Matchbox 1/72 kit of it. It was a respectable and certainly workable kit that came with some nice options like wheel, ski or float landing gear and both short and long nose cones. It came with Canadian military markings and a civilian option, Aurigney if I recall correctly.
Modelcraft has a 1/72 Twin otter new to their catalog, I don't know if its a new tooling or the old matchbox, but the picture of the box art shows it in Norontair markings with that nice stylized loon motif on the fuselage sides.
If you get your hands on either kit, I've slapped three photos of Canadian military "Twotters" in the aircraft reference photo section of the free photo gallery RonUSMC is offering in General Modeling Discussion forum. Detail speaking, there isn't a whole lot of difference between between most civilian Twin Otters and the Canadian Military ones, so if you ever wanted to detail one, those photos might help you.
Woody:
You're so right about civilian aircraft being pressed into military service.
The Beech 17 is just one, others include:
The Dakota, she was the DC-3 before she was the C-47.
Beech 18s became C-45s
The Beaver and the Norseman also got militarized.
The Pilatus Porter, still a treat to see one lift off, military or civilian.
Airliners have always found a way to get into uniform, even today.
VC-10s and Lockheed Tristars that once flew passengers soldier on with the RAF as tankers.
The DC-10 does the same tanking duty for the USAF and I think a few others now
But the major tip of the hat has to go to the 707. Oh the things she's been put through when in uniform, the KC-135 was just the begining. She's been the basis for a series of special mission aircraft that have used the entire alphabet and then some in prefix and suffix letters to tell them all apart:
E-3, E-6, E-8, KC-135, RC-135, NC-135, EC-135, VC-135..... She's still the old 707 under it all and being the 707 is all she needs to be to be a beauty in my books.