Hey there, although the idea of a "exchange X amount of threads or cloth for Y" might sound very reasonable, there are a lot of important details to keep in mind. For example, how difficult is it to obtain the Y piece? What should the X ratio be? To give a very simple example of why an exchange systems might be tricky:

Trade all your Zabuza fragments for Itachi Susanoo ones! Obviously, Itachi is a LOT more difficult to get than our good old Zabuza, so that type of system is very awkward to introduce.

There is also the fact that Oasisgames is a publisher of Naruto Online, not the developer. While they are working directly together with the developers, any changes to systems like this would have to be discussed first internally to see if they have merit/would work, and then actually redirected to the developers.

So while we do take suggestions like this into consideration, we obviously aren't always able to act upon them.