Hey, AuroraKTA!
In my opinion, the essay would still be thematically structured - as it is the most logical method to address the aspect of "reframing" a text. However, the use of "novel form" or for a fact if any question had a technique (e.g. intertextuality, allusions etc) - you just needs you to focus on a particular sub-set of techniques as you analyse The Tempest and Hag-Seed, this includes (for your question):
- Free Indirect Discourse (allows us to see the compartmentalisation of Felix's mind - and how he copes with grief, humiliation and revenge --> something which Tempest wasn't able to effectively do).
- Greater visual imagery, use of metaphors, allusions, chapters, epilogue and prologues - that aren't restricted by a dramatic form - it allows Shakespeare's story to be opened for interpretation by audiences and the simplistic stage direction of The Tempest, is in some ways "revolutionised" by Atwood's transition to a novel.
You can find many more form-related techniques that make the novel the most appropriate method to disseminate to the masses, especially for a modern audience, as that's the form that we consume information (compared to Shakespeare - which were largely drama/plays).
angewina_naguen brought up some very good points, I would just add to make sure you show similarities and differences to have a more holistic analysis for each technique/concept. The main thing you need to really achieve is why Atwood made these changes - some are just pragmatic but others ideological and contextual. Good Luck!