Loooooong ago, before the commendation system, I had suggested using the mailing system (because I really want that to be a thing in the game lol) to receive other worldly letters with gifts from other players who liked your presence in the dungeon/content (none of the reward token ideas were this creative though, it's a nice list). One of the reasons why it was to be used to mail, not sure if I made it clear when posting at the time, was by not having it at the end of dungeon you could separate the issue of only having one free gift to give when there were more than one in the group (so like a day or two later you'd just get mail from another world). Also then it wouldn't be important to quickly pick who you liked because it's not like they received the 'commendation' right away anyway. I don't think I had thought of it at the time but having these delivered in bulk would have been smart, .. maybe because the game was less popular at the time but that'd clearly not work singularly delivered commendations in the mail lol. Anyway, these void gifts could be used to buy other things. In my mind a moogle would have been more important than they are now, so you'd get kupo feedback talking about good a person you are and cute stuff like that lol.
Btw I really like the echo idea. Blue Mage, for the most part once you get both a spam-able heal and healer mimicry (with basic, which is easy to get) becomes really strong solo but one idea had been an incense they could burn to greatly enhance their power (made by beast tribe quests) for solo content sync or doing like raid content unsync (1 person doing a 24 man content lol).
I have had reservations about some of the rewards and maybe people turning this into the new "Mentor" thing.. just seems like a few bad apples are going mess it up.. but in a vacuum at least I read the idea and think that'd be fun.
I really enjoy the ideas of people rewarding each other like a Death Stranding system. Wonder if there might be some cute mechanic in pay it forward where there is a chance a pay it forward commendation replicates itself into that person's possession (such that they can then pay another forward, not crazy high chance but still).