When you start playing piano as a child, you become (by same practice) a
better pianist than a person who have started at adult age. This system
transported to batworld could be like:
-You would get bonuses from your first guild. Good skills, better masteries,
etc.
-You would NOT get bonuses from your second guild. Masteries could be a lot
smaller, you wouldn't get so much stat bonuses etc.
This change could encourage us to create parties with miscellaneous people
(which Naked mentioned) because getting a highly optimized party would be
harder than before.
ksahn