It sort of depends on how much they're offering. Hiring contractors to build features might be an option. (As someone who's been freelance it's rather common practice)<p>An alternative is to spawn a new UX to the app... Be careful here.
At one place I worked we spawned a different private version of our app that made it possible for big clients to whitebox. We called the team "commercial".
Different UX, different pricing for users of the different UX. It worked rather well. They paid for the changes to the UX for their "white box".<p>Where we went wrong. We should have called them markets. That is my one bit of advice. Call the different UX a different market.<p>Then you get something for free. You get to go international. Instead of just "Wallmart" being a market, and "Target" being a market. (with different language, different fonts, and different assets (including emails). You GET UK being a market, and Sydney being a market, and ...<p>If you do it right, you have a pattern for building things for different business, and different geography. Win win.<p>Final cheat code.<p>If you eventually plan on breaking your database into many different DB's don't go fancy on the user_ids. Just change the sequence to increment the ids by 100, instead of 1, and all users built in region/market 0 get n00, while users built in region/market 1 get n01, and so on. It's not so you know where the user was built, it's to guarantee uniqueness of the ID. It's a pile easier than changing your whole system to UUID's.