I have a trending line chart, and want to give the users an option to change it to a stacked bar chart if they prefer that view better. Is this possible?

You could try utilizing tabs in your report building in TBM studio.  The first tab could be bar chart and the second tab could be line chart. 

Thanks for this great idea! We already have multiple tabs on this report so I think it would become too "bulky", looking for an option like a Parameter or radio button to toggle back and forth if poss

Unfortunately not, @Rachel Yaghoubzadeh. Have you check out the Self Service Reporting by Apptio -- Create a self-service report ? That's probably the closest you get to letting the user choose what chart they would like to view.

Good idea, @Tony Wong. I believe it only works for Cost Source, though...