I'll buy some if they are being traded in a caravan, but I won't embark with any.
If you add the wood ethics back in, and change the title of the "tax collector" to "merchant's guild representative", then their job is just to tell you whatever is happening in the world around you rather than facilitate trade. Maybe those are the items that the fortress is allowed to trade with other nations. As a kind of "price fixing" using "artificial scarcity".
However, that also means that the fortress will no longer host nobles or be able to become a Mountainhome, since that's coded to flag with the amount of excess income a fortress gives to the caravan over time (as well as number of jobs during the visit)
Gremlins are sellable by caravans and also can arrive as pets of migrants. But, as I know, you need to embark with trolls, because they have only SLOW_LEARNER, but no PET or PET_EXOTIC. If you dislike exploits, add [PETVALUE:350] to trolls and [PETVALUE:25] to gremlins. Or you can add PET_EXOTIC to trolls, this make wild trolls trainable and caravans will sell caged trolls, but this may cause bugs (I don't know serious bugs, but gremlin who arrive as migrant's pet cannot work even by DT).
Wood ethics works fine. Bug was caused by animal killing ethic or combo of this ethic with one other ethic. I don't test much. Maybe, there will be more interesting way to solve the bug without exotic experience loss.
So, if trading is so important, will be better to not remove it from civ. For nobles, I have an idea to promote them without trading. Any other benefits from Mountainhome status?