Picking up on the idea mentioned in the now completed audience viewing mode ( http://help.slides.com/forums/175819-general/suggestions/4440978-leader-audience-viewing-modes / http://help.slides.com/knowledgebase/articles/333924 ), I'd like to see a feature that embeds interactive polls in the audience view, show the poll result on the main presentation screen (or maybe on the next slide, to avoid viewers answering based on other voter's answer).
This might easily get out of scope, so maybe embedding a third-part solution via iframes can be demonstrated/promoted.
Ronai Lisboa commented
Something similar to the H5P.org to embed pool, answer-question, multiplechoice, etc.
Mentimeter.com allows one to create polls & Q&A stuff, and one can link to specific results slides. Very cool integration!
If voting doesn't work for you after embedding a Mentimeter poll page, and you happen to be using Firefox, allowing third-party cookies might help :)
I'd specifically request integration with PollEverywhere (https://www.polleverywhere.com/), though that would likely require partnering with them, since just an iframe doesn't support the "full-screen" view.