If the suggestion goes through, why not pay with pve coins instead of pokedollars?
Make it a goal for guilds to reach. Perhaps the top 3 guilds with the most pve coins contributed by the end of the season will have access to the island. It would be fun to see guilds competing to see who can contribute more pve coins rather than pvp rating.
This way, the guild island still keeps their exclusivity, while being able to give pve or non-pvp focused guilds a chance.