It's noticeable that the Faux Hero, who gives you the Friendly Tokens at the front of the castle, only reacts differently to three outfits: the Timeless Tunic, the Tri Suit and Linebeck's Uniform. The first two are gotten from Friendly Tokens and it makes sense that he would react to them, but why also to Linebeck? Maybe this costume was supposed to cost Friendly Tokens as well, early on I speculated that there would be a costume costing the remaining seven tokens, which was before I discovered that you could sell them.
Also, with Linebeck's Uniform it's possible to read the secret message down at the water. Only the Tri Suit let you do that so far and the message was supposedly only readable by someone with many friends, while Linebeck is more of a loner. So, thematically it doesn't fit, which might be another hint that Linebeck's Uniform originally was supposed to cost many Friendly Tokens.
Other than that I also collected all 15 Friendly Tokens from the kid by now. I farmed them using all my 3DS systems, because the Zelda fan meeting later this month sadly got cancelled and I didn't want to wait until summer, before I was able to complete everything. And I still have another copy of the game, where I could collect them all over again. But with that I have 100%ed this game so to say. At least until the next big update hits.