This would've worked better in 4.84 when you still had niobium/diamonds, there are some good routes between rheinland and kusari, but I'm not sure they're that busy, as I explained in another thread BretoniaRheinland trade is crap, and pirated heavily, with the zoners/slavers issue currently in 4.85, or anyone who can feasably run dueteriumcounterfiet, or slavescardi, noone really NEEDS rheinland, except blockaderunners (which is all you'll probably get) or real traders, traders that somehow stick to the poor profit and high piracy routes for the love of their factions, and it'd punish them.
Though actually I'm tired, and I think this might only effect LibertyRheinland? Might be ok that way, but taxing the bad trade routes is not going to help, wait until those runs are better than the two runs I mentioned, then you might have something.