Yes, that’s a good approach.
I’ve used that approach on Topic List Previews for a while now, moving as much of the functionality into the TC as possible and making it stand alone. Additional features which require API modifications then go into a plugin and users are encouraged to install that too to take advantage of them (if they can).
The only issue with this approach is if you are sharing your code and API modification is a necessity, then you have to make sure someone installs both components. Splitting them into two is not the most convenient way for people to then consume your work, potentially, so I still think that ultimately a single plugin install is still the best approach for open source work of that nature.
If it’s just for your own site, then sure, this is great!