You seem to be assuming that you are the only person who will ever contribute meaningfully to the software. But if, as you probably also hope, the software is widespead and successful, there will most probably arise at least one popular third-party extension/modification. And you will not be able to incorporate this addition into the product which you distribute to your b2b customers; this will make your version of the software inferior to the free version.
The other option is that could simply pay community members some fair portion of the b2b revenue in exchange for signing the CLA. If you're the primary contributor, it's fair to take most of the revenue for yourself, but revenue sharing with major contributors from the community is also fair. Could be difficult tax-wise though? IDK.
The most difficult thing might be to have all parties agree to what, exactly, would constitute a fair arrangement. Free software where nobody gets directly paid is one thing which is easy to understand, but if money gets involved, things tend to get ugly, and nothing destroys a budding community faster than bitter infighting.
