I think that is the general conclusion, Ming. I would go with the ideas that Lily99 and Cym Ladye posted, planting your phals in separate pots and then placing those pots together in a large decorative container.

The risk of disease is a real concern. Another is the fact that planted in the same pot, they may or may not decide to bloom at the same time. Putting pots together is a great way to go since you can pick and choose what ever is in flower at the same time.