Javascript App in member only post through custom theme or Any better way?

I am a newbie here,
I have a Blog in Ghost starter plan.
I am planning to Convert the Website to a full Membership platform.

please advise me on how can I implement the following features in the Ghost.

I want to know is it possible to have these features through Custom theme Development or by any other way of adding Javascript apps?

  1. Need a Javascript app inside the membership area, in the post, which will play media (sounds & animations) according to the user feedback through Bluetooth device integrations with the App.
  2. Can we use the ‘Tag’ for configuring the App feature. eg for each specific tag, the Javascript app can be configured differently.
  3. The expected Feature of the App is to give live feedback according to the Bluetooth Data received. is it possible to achieve this through a Custom theme?
  4. I am don’t know, if there are any limitations for achieving the above through a custom theme, please let me know if there is any better ways or limitations?

thanking you in Advance.