It's golden this should be suggested by the one person I have met in this game who push the rules and work with every little crack and flaw this game have to give him an edge (and have kingdom members repeatedly banned for multi-accounting, as encouraged by you). Ideally it's not a bad suggestion as such, but the implementation is next to impossible, we both know that if anything similar to this were to be implemented, you would be the first to abuse it and create a ton of wings and use those wings to boost your treasure count past what a "normal" kingdom would be able to do (Just like you normally do, with alt kingdom's robber camp spawns). To top it off this is exactly what should NOT be done, if a game wish to have new players introduced and hooked. It won't take long before every kingdom have a core group, and won't invite anyone into the kingdom UNLESS they have played previously and/or are known friends of the people already in the kingdom, it would turn the whole game into one big "I rub you, you rub me". AKA this "idea" would literally kill the game. (Like how you killed the interest your own kingdom members had for the game, by rotting them in a giant server wide alliance, that ended up loosing big time anyway).
Just my thoughts on it. =3