I like your approach. I've thought of it in those terms before too.
There's talent, there's pure need, and there's positional value.
I, however, would like to challenge your assertion that the positional value of a LT is higher than that of a CB. I tend to think you can arrive at many truths by following the money.
In the NFL, you can tell what positions execs see as the most valuable by looking at which positions carry the highest salaries. As one would expect, QB and pass rushers are the highest paid positions followed by DT's, WR's, CB's, and LT's in that order.
I maintain that that salary info suggests that CB's have a higher positional value than LT's.
FWIW, when you talk about the dangers of an OL implosion, you're talking about pure need.
