i don't know what kind of amounts of wealth we are talking about
but does it really matter what castle you spend your wealth on ?
the way the game works right now is that wealth dictates your speed of progression
if you share wealth you could accumulate 200 wealth on your 1st castle and then boost out your 2nd castle in a matter of hours
atm you could only do that if you are willing to invest real money into the game
but if you share wealth over your whole account only the first castle will be a challenge
+ it would cost the devs potential profit cuz why would one spend money on wealth if you can just use the loads you got spare from your main castle
just pick a castle and use the wealth on it... and get the other castle up without it
i mean iv build my human castle up in a few days without buying or getting any wealth... and i don't know why anyone else would need extra wealth
the game gives you plenty... iv even got a royal dragon without to much work...