Semi-random thoughts ...
Semi-random, so IHMO:
...
So ... if a character spends time beforehand finding a great hiding spot,
say, behind a stone wall, wouldn't finding that spot be the equivalent
of gaining a circumstance bonus?
I'd imagine that a character that dons camouflage netting is gaining
a bonus to their hide check. A character that removes all shine on their
person should gain a bonus. (Remember: Shape, Surface, Shine, Silhouette,
Shadow, Spacing and Movement) Hmm, unless that is what the character's
hide ability represents ... their ability to know these factors and minimize them.
...
The problem that I'm having is that the spot DC should be less random
than the spot vs. hide mechanic makes it. Spotting your fallen
comrade, who was wearing a brown and green outfit, and who fell
into a clump of similarly colored foliage, should not take a spot check
against a hide ability. It should have a fixed or nearly fixed spot DC.
(or a pseudo hide roll, based on the circumstances?)
On the other hand, spotting a bright blue character in front of a yellow
background ("in plain sight") should be and is automatic.
...
I'd imagine that if a character has time to setup a camouflage blind, and
steps out to check on the visibility of that blind, should be able to set the
spot DC to their own best spot result. The time to setup the blind should
be longer than 20 spot checks, since they have to go back to their blind
and adjust between checks. And, the blind should definitely be directional.
(Ever watch a magic show from *behind* the magician? You see a heck a
lot more of the mundane mechanics of the tricks.)
...
In a case where the hide result cannot be checked, say, if a character dives
behind a log into a pile of leaves and has no real idea of how well they hid,
then a single hide roll to determine their spot DC -- with modifiers according to
how much cover the leaves might actually provide, and according to the
characters outfit, and how good they are at burrowing into the leaves (their
hide ability) -- seems appropriate. But whether they hid well (burrowed deeply)
or poorly (left their butt sticking out) would be according to a single roll.