Advice asked: is the standard post format extensible with taxonomies?

Hi there,
My new customer doesn't know exactly what she wants yet. There is a chance that the standard WP post functionality for her new multi-author blog will be sufficient, there's also a small chance that there will be needed extra taxonomies/tags functionality.

When I use CustomPress, can I add these to the standard WP posts when they are needed?

Thanks for clarifying!

CHeers,
Ronald