Disagree. What does it meant to have Basecamp with "more features"? Features aren't in themselves good things.
Instead, you end up needing to focus the new features around a particular theme or value proposition- be it better collaboration, or better security, or whatever.
And then while you're adding features in that direction, oftentimes you don't need to implement the full Basecamp featureset. You just need to be better in a direction that's valuable and enough of the base featureset to have an OK product. Seriously, it's not a good idea to start up a new product and expect to build all of Basecamp AND add new features and be successful. That'd take years to even get the first version of the product out. Avoid unless you have millions in funding and an excellent team from the get-go that knows exactly how to execute this strategy.