MM4,
I find nothing to disagree with in what you say and I might not have articulated myself very well, as I think we're essentially saying the same thing.
My aspiration for SDSR goes like this:
1. Decide upon and define the threat.
2. Decide upon and define the necessary stance to mitigate that threat.
3. Cost it.
4. Adjust according to budget.
Unaffordable capability is not capability.
Point 4 involves describing and then understanding and accepting, any 'capability gaps' (we both agree that's a crap term) that result.
Sun.