Perhaps there is a workaround solution, like a hotkey that could handoff to Mac's native QuickLook.
I often preview a document in Alfred, find what I need then move back to my application, but about a third of the time I come across a long phrase or unmemorable string of numbers/text that I sure could use the ability to copy before moving back to my current application. Instead I have to open file, copy, go back to application, thus disrupting my workflow and focus. It's not the worst, but this would make it more seamless. Using a hotkey to achieve this would not be disrupting.
Anyway, I appreciate that you're looking into it.