Seems like an over-convoluted solution if you ask me though.
It's possible to put a threadfield into the display format of another (it's a "hack" where you need to set the display ordering differently).
Eg
Image: display order = 1, key = img, display format =
URL: display order = 2, display format =
Note that the display order determines the order in which XThreads evaluates the display formats, so you can only make references to items with a lower display order.
I never thought managing threadfields was particularly time consuming so I don't really see much time saving there. Feel free to explain otherwise though.