I tried previously to find a plugin for Illy that pulled in the data similar to Flexi, to no avail. At least at that time.
What I ended up doing is building my template to suit (meaning set it up how I actually use it in Flexi, Because we use both here) Then exported all the versions of it from Flexi as PDFs or EPSs. In my case both 8.5x11 and 11x17. Then place them on a separate layer in Illy. Then when it comes time to send a proof I just print the entire page/artboard. It actually works really well, albeit a pia to fill in all the data by hand (but hey whats a few extra keystrokes). And if you are working with something large, or better stated, larger than your proof sheet, just scale up the proof sheet. As long as the proof sheet stays the same height to width ratio, the resulting PDF proof will be sized properly (8.5x11 or 11x17). Hope that helps.