Well given the current system the only thing you really need your guild for in this game is GWF to get the buffs and to sail. So yes there needs to be meaning to have a powerful guild. We need something to fight over. The problem is some of those buffs just overpower a guild when they hold all or most cities, therefore competition dies.

Attaching the current buffs to your guild level increases competition on the server, but makes having a guild meaningless, because if you start from day 1 of server you could easily get your guild level up with yourself a few part timers and alts.

On some servers GWF is meaningful and people like playing on a server where the buffs are not guaranteed.

On other servers we have 1 guild holding all cities

SO to make a change that effects all servers in different ways is not the answer.

However adding more guild events is a good idea where coins/creds/rep are the reward only
Adding a buff to guild level would be nice. Perhaps cut all current buffs in half - the city gives half the buff, the level gives the other half - May work or some servers - may not work on all