...actually, there's one room in the armory I didn't search - the room with laser traps that look really difficult to avoid. Guess I'm going to have to either navigate past the traps, or trigger the traps and hurry to safety. Obviously the former is preferrable, but the latter will be done if I fail to avoid the traps.
Also, when Psycho Mantis told Snake and Meryl the path to where Metal Gear REX is being stored, he remarked about "glaciers in the way", which couldn't help but make me think about some environment-related gameplay mechanics in the sequels, such as how weather apparently factors into MGS2's gameplay (not sure how that works), and the camouflage systems of MGS3 and MGS4.
To be fair, MGS1 is already making headway here with stuff like guards following footprints in the snow...