Has there been any thought given by any of you of taking the Imperial variant and adding more trade decks on the top rather than looping around as is currently done (basically 10+ decks)? My gut feel is that it would be a horribly bad idea, but I don't have any reasons to back that up yet.

I haven't thought about it, but my first impression is way to valuable cards.
Though I suppose getting a full sett of stack 18 cards would take you a while...

Well, looking at things more. If you were to follow the current track, you are looking at a 3/4 card count in the 10 deck too. Which, meh.

Well, not quite. There is one stack with 6/7 (5th), and two with 5/6 (6th and 7th), so there should logically be three with 4/5 (8th to 10th), four with 3/4 (11th through 14th) and the remainder with 2/3 (15th through 18th).
But still, only a single card of the shared commodity in each of the 15th through 18th stack.
Perhaps not too much value after all...

Well, we better can compute this different. The highest total value of an set now is 256, the value of 8 cards from the 4th stack. We can keep holding the same numbers of cards from a higher stack until the maximum value of 250 points is reached. And afterwards reduce the number of cards by one:
Keep the 4/5 cards from stack 10 having a maximum value of 250.
Make 3/4 cards from stack 11-16 having maxima of 176, 192, 208, 224, 240 resp 256.
Make 2/3 cards from stack 17 and 18 having maxima of 153 resp 162. This is not much, until you can add the face value due to receiving cards from the other area.

There is only one other problem: The calamities. From stack 11 on it is impossible to make the first 8 cards being commodity cards. In addition, we have to make new calamity cards to put in stack 11 till 18...