Using Javascript popups to create a workflow for legal experts writing and editing legislation

I suppose this is a ui-flow question.

I'm currently working on a project where a couple of the stakeholders are suggesting the use of popup windows, i.e. browser tabs, to create a workflow to switch between and compare multiple texts. For example, the user might open several pieces of legislation to compare them. They might also want to open different legislative vocabulary items to compare their connections.

Right now, the suggestion is to open each of these pieces of legislation / vocabulary in a new browser tab so the user can use keyboard shortcuts to navigate between them. To me, this seems like a bad idea, as the user will constantly be navigating away from the main app to access resources. It also seems very disorganised from a navigational standpoint, and from what I've read, it doesn't seem very plausible to force the creation of browser tabs for every browser.

Does anyone have any advice or caveats about creating a ui-flow using pop up windows?