I guess, distilled down to a single question, how do we assess the value of BTC as if it were completely decoupled from any other currency? Or can we even? Are we just seeing a raw, uncluttered effect common to all currencies, with the effects magnified by other variables in the BitCoin system?
Sure you can. How do people asses Labor, how do people asses Drugs , How do people asses ideas? You can asses them in whatever currency you want BTC , USD , Both, and to whatever value you want. The exchange value only matters if you need/want too exchange the BTC for USD or USD for BTC. It represents one simple thing : What value of USD/PLN/EUR someone was willing to give away for one BTC and vice-versa .
If you need USD for resources you can always speculate and asses the BTC at higher values and ask less BTC for a certain product/service , or more , depends on how you asses them. And then all that matters is how the customers will asses your product. If your assessment and your customer's assessment are close then the customer will buy.
But right now the BTC economy is quite small and it is mostly based on the exchange value because most of the BTC economy is composed of mostly traders which buy with dollars and add a small commission and then convert that value to BTC . If there were more producers and service providers assessing their products in BTC then the economy will move from one based on the exchange value (couplet to other currency) to one based on the assessment of BTC/PRODUCT and BTC/SERVICE.