I think this sort or thing is always welcome, so congratulations.
Having said that, when I upgraded from IPS 3.x to 4.x, I ditched Tapatalk, which was the only app available around that time.
I thought it didn't make sense that Invision Powerboard had become Invision Powersuite, yet the app was absolutely forum-centric. And being the responsive version of IPS a great improvement for mobile users, the only thing we actually regretted losing was the push notifications. Which, admittedly, for some was a bigger deal than for others.
Another reason for ditching TapaTalk was that (at least up to IPB 3.x) TapaTalk couldn't even show polls, let alone a data template that we have added to topics in some subforums. (3rd party application)
But something good TapaTalk has or had to mitigate this, is the ability to prevent posting in selected subforums. I say this is good because if you wish members to post yes or yes using a 3rd party plugin like the one we have or any other template, etc, in selected subforums, you rather have them using a web browser where the plugin works, even if it's linked from the app, like it was the case with TapaTalk, and like you say it will be for other native areas of the Suite with your app.
So, I beg you to add this function of blocking posting in selected subforums using the app directly, particularly if you won't release the code for 3rd party plugins development. (And while you are at it, please remember that excluding subforums serves more forum owners than including subforums when selecting, particularly when you have to click/tap one by one. Excluding serves those forums with any number of subforums, while including only serves those forums with just a few).
Obviously, it would be great if you also give admins the option to enable the app or not altogether (and I think you've already said you will). I really would like to have push notifications back, and being able to give users the alternative of using the app, but at the end of the day, its use in our forum would be conditioned to the above factors and probably others too. I look forward to it either way. Keep up the good work.