Important: This is obviously a big feature, and big feature means it needs huge support.
To arenanet: If there is any reason why this won't be in game, please tell.
I know this will probably never happen. Hovewer, this game desperately needs a test server (even if it's only HoTM). I will not say anything too detailed because I don't know how the engine works.
Since anet showed they are willing to do hotfixes, it's a good idea to have either closed testing (random players in various ranks get invite from anet) or open testing (every player gets a certain amount of non-recurring time).
% Ability to give feedback about traits, skills and mechanics (obviously)
% Ability to queue in some way
% HoTM only
% Since we get to see the patch notes in friday, test server could be available in the weekend after a patch note friday.