What if I add maltodextrine to the equation? Is there a ratio of MD (or other adjunct) to LME that could be used to approximate the fermentability of pale malt at various mash temperatures?
I see your point here, and with the original post in general. I have been wondering about this same topic... mash temp and extract. What I was able to find out is that the fermentability, body, mouthfeel of your extract is going to depend on the type and the manufacturer. With extract, you are subject to whatever the manufacturer mashed at and what ingredients they used.
With the variance from type and manufacturer, I think you have a few possible alternatives:
1: Try it yourself. Try a few different extracts and see what kind of body, mouthfeel you are getting. However, this option takes time, money etc so you might want to skip some steps.
2: Look at the databases or forums posts about the different types of extracts. I am sure people have taken detailed notes on the profiles and mouthfeels from different extracts. My guess is the darker the extract, the less fermentable, more dextrinous it will be. For example, Briess Golden Light (4lovi) vs Briess Light (2lovi... I think).
3: Call the manufacturer. I have thought about doing this and could either be very helpful, or not helpful at all.
4: I guess adding maltodex could help compensate, but I think you would get fine results with the right extract, making that addition unnecessary.
Good luck to you sir, and let us know the results!!