Alternative to lack of Storyline responsiveness: vertical slide decks?

Hi all, 

At my current company, a great learning experience design studio, I am facing a major barrier: resistance to Storyline assets. We have had success sticking to Rise due to its mobile responsiveness since most of our clients' learners (75%) have their learning experiences on their mobile devices. 
Next Friday I scheduled a pitch meeting with the CEO to show the benefits of using Storyline, but it would be really great if I could address the responsiveness issue because it is the main blocker. 

I thought of developing the same asset (that we already have content and visuals for) twice: one in a traditional horizontal layout (16:9) and the other one for a vertical mobile experience (9:16). What I'm unsure of and would love some help:
1) Is there a way that I can have different slide sizes in the same project? That would be ideal because I could create two branches, each in one of those sizes, and have a button in all slides so they can click to switch between vertical and horizontal at any point. 
2) If that's not possible, create two separate projects, and that's where it starts getting trickier. Could I - have that "forever there button" to switch from the horizontal to the vertical projects - capture their progress and transfer to the other project? Or would the learners have to commit to one of the formats and take that all the way?

3) Any other ideas on how to deal with a situation like this?

Thank you all for your help! :)