With the rise of the new dye kits and relking coins continuously becoming more useful, I would love to see an option to list things in merchant and rancher shops for either Tu, CP, or RC. The exchange rate for these currencies are already pretty standardized (1mil = 1CP, 1RC = 300k) so I don't think it would affect things economically. However, it would greatly improve the ability for users without access to the shoutbox to make these exchanges, as the trades don't seem to get much traffic from my observations.
I imagine it would look just like the shops do now, but with an additional two columns under price. One would be for relking coin prices, another for CP. There may also be options for "and/or" pricing, so it would read like "10mil tu or 33 relking coins" or "5mil tu and 16 relking coins."
I'm not entirely sure how the and/or would work with having three currency options, though.
Perhaps there could instead be a column for numeric value, then a dropdown for the currency types. Not sure what it should look like, but I think it would be very helpful!