Why? You've had a 645D and 645Z so far, plus the GFX. The P30+ is an older chip than the 645D, same microlenses on a CCD chip. The DF is not what I would consider to be a great body, especially given any type of travel. You'll be working at base ISO as much as possible, so ISO100 & most likely having to double/triple check autofocus.
What makes it appealing to you? Is it the resolution, colors, camera in hand type stuff? If it was a steal of a price, based on what has actually sold on ebay, I may consider picking it up and trying it, knowing I could flip it for minimal loss.
If you were adding a P30+ as a digital back but would mostly shoot film, I would fully support it. If you're going to shoot digital only, there is nothing appealing about the P/P+ backs other than the P45+ and P65+. Any perceived savings would lost with a single issue in the body (cuz the back won't die, ever).
Best of luck,