If customs duties act like a domestic tax, wouldn't that mean that they should initially be considered neutral? They would then be another type of consumption tax. Any assessment would have to be made in the context of the tax system as a whole. Are consumption taxes too high overall? Too low? Or just right? Who pays the taxes? Is that fair? Who and what are the taxes collected spent on? Etc.
Neat as in fantastic - it literally can't get any better - for the oligarchs. Tax the poor, and tell them we're collecting money for them, from the foreigners.
Raise and lower the rates willy-nilly, no need to really justify why you're squeezing who.