I think it's a good idea. I think the different guilds would be a great place for that. Since they got rid of guild marks is there really any reason to go to the individual guilds in the first place?

Even if they aren't implemented in an open setting allow us to have some in our linkshell/company/personal housing areas. Also include a comprehensive battle tutorial/sequence in each of the guilds for new players as well. You could even make it a low level achievement where you trained on each dummy in each guild as the guilds corresponding class.