I agree with your process, in general. Like I previously said, there often becomes a butterfly effect on these things that makes the impact of a trade last decades until it's complete.
Of course we all evaluate a trade when it happens and I try to put an estimated weight on the unknown varibles in the future. Whether that be future picks, potential, injury history, etc.
I think it can get complicated on trades with draft picks because I'm not sure a GM should get credit/punished if the pick turns out to be abnormally good/bad down the road. For example, if in the spring of 2007, we traded our 2007 unprotected pick for Udonis Haslem, I would say that was a bad trade. The unknown at the time would be that our pick would turn into the #1 pick, and that consencous #1 pick would be Greg Oden, etc... Despite Haslem having the better career than Oden, I would still say the trade would've been bad move by Steve Patterson.
On the flip side, I'd say people would over-state how good the Gerald Wallace to the Nets trade was for Portland. Wallace for a pick between 5-10 in the draft was a good move, no doubt. However, I can't give the GM credit for knowing Lillard was their guy and that he'd be available. I'll give them credit for that selection seperately, but not bonus credit for the trade itself. If that makes sense.