It should be fairly simple to do this step, as you should already have an idea of what you haven't written down in either step 2 or step 3.
For my current project it was only Text to Speech that isn't critical. I do want to implement it in my app at some point, but it can come later.
It is recommended to do a bit of research on these features to see how hard they are to implement. If they are easy enough, you might want to implement them instead of adding them to the todo list.
I did quite a bit research on Text to Speech, and it's fairly simple to implement if you aren't using a framework, and are coding native on at least iOS and Android, but for frameworks, it still looks like a no-go. However, there are a few third party companies building TTS engines that might work for my app, so I need to see have hard it is to create a plugin/module for any chosen framework as well.
This leads to adding a feature to step 2:
- How hard is it to create plugins/modules?
I'm not updating step 2 with this, but I'll keep it in mind when comparing various frameworks.