I picked-up a Minolta XG-1 kit at a rummage sale about five years ago... nice body with the motor-drive, 28 / 45 / 50-1.4 /100-220 Zoom, several flashes, couple of convertors, etc, for $50.
It is my "new" SLR outfit. The glass is all hard to beat, and still plentiful through dealers in used gear or e-bay.
The down-side to the XG-1 is the electronic shutter, and the LED display for the meter. It will operate as Full AE, Aperture-Priority, or manual (using the TTL meter in the camera).
I just received a Minolta SR-1 from e-bay, that I bought primarily for the vintage Heiland Strobonar (pre-Honeywell) flash that was being listed with it.
I was pleasantly surprised when I opened the box and started checking-out the camera; it is a SR- 1 b, from about 1960, and is a full-mechanical, manual SLR. Heck, it doesn't even have an accessory shoe on the body !
There was a clip-on shoe that mounted over the prism housing, and a meter that clipped-over the shutter speed dial, like on a Leica M.
It came with the original Auto-Rokkor PF lenses, a 35mm f:2.8, and a 55 mm f:1.7. It will accept just about every MC / MD lens made since.
The SR series was made from 1959 into the 1970s, and were good yeoman cameras with decent, fast glass, and bright finders.
The earlier SR cameras did not have aperture pre-view levers or mirror lock-up; and models made before 1963, the aperture did not re-open to full until the film was advanced to the next frame.
I went looking for several more early minolta SLR lenses and found at least a dozen on e-Bay, few listing over $100 USD.
I've been very pleased with the pics from my XG-1; I am planning to hacve this SR-1 CLA's and shoot with it... goodness knows I already have plenty of glass that will fit.
Can't knock Pentax; good stuff, many professional photogs in my area used them, one guy even wore-out several Spot-matics !
As for finding a compact/light-weight SLR... that almost seems like a contradiction. But maybe I'm spoiled by all the screw-mount Leicas I've been playing with lately !
I think I'd vote for either the Minolta or Asahi-Pentax, in a pure mechanical... it can be CLA'd for generations to come... if you've got the bucks, the Nikon /Canon are excellent too.
Good luck !
Luddite Frank
( Or you could come over to the "dark side", and get an Exakta !!!! )