I dunno, but I thought that using guildmarks to purchase abilities was actually a pretty decent way of doing things. I would have liked them to just expand upon it further by:

- increasing the ways in which one could obtain guildmarks
- adapting some of the better features from FF11's merit point system to the guildmark system
- increasing the amount of abilities, traits, and skills one could purchase
- adding unique guild-related items that one could purchase