Acknowleding the criteria you laid out for us, i also concur with 2F/2F that the complete lens/accessory system that must be a foundational consideration in every camera body selection.
Any of the 5 "mainstream" brands listed above (Canon, Minolta, Nikon, Olympus, Pentax) present excellent offerings. I'd be remiss if i didn't mention the commonly acknowlegded "upscale" brands as well - Contax, Leica, Minox, Zeiss, et al. if you are so inclined. There are also several "less-mainstream" brands such as Fujica, Praktica, Ricoh, Yashica, and Zenit that also offer excellent cameras and lenses. However, it is the entire system that is of most significant interest.
Incidently, i don't subscribe to the ideology that a person's chosen system must have the absolute broadest offerings; Rather the BEST offering for your currrent desired style of photography, but also one which has the capacity to grow with you.
Like you, i also like to photograph outdoors so i needed a system that can operate in cold temps. Since all camera systems have this capacity if the user is careful, i began my selection process by whittling away at the "look" of images the different manufacturers - each manufacturer seemed to have a different approach/goal to their lens making. Since i was already familiar with the Minolta system via the X-700 (for me, NOT a good outdoor camera body), i was advised to check out the more rugged Minolta SRT series bodies (all manual except the light meter which requires a battery) which has turned out to be a perfect fit for my outdoor criteria.
Providentially, I had also developed a deep appreciation for the look of Minolta Rokkor optics so it has been a good fit for me as i have meandered further into photography. I now use Minolta XD-11s (with the same lovely Rokkor glass) almost exclusively except when on "cold" trips or my dSLR is needed for speed.
I can buy some truly magnificent Rokkor lenses for usually well under $200 and frequently under $50. Also, the Rokkor lens line-up is broad enough to accomodate anything i will likely ever want to do.
YMMV....