That's the thing. It would just be a GAS and experience buy for something between £300-£500. On another day I'd just buy another manual lens
I do prefer FF as I can use my manual lenses but MFT is useful because it's small and responds like a sports car so a Fuji would be an addition and wouldn't really replace anything and certainly not everything. I can see the point that it could be someone's only camera and that does appeal to me as I'd be going back to how it all started for me with a Kodak Instamatic but I'm not going to go that route today.
I do remember downloading some Fuji files years ago and not being impressed but the ones I've downloaded today do look good but that could be because I'm processing them with new software. The A7 isn't going anywhere and looking at MFT at 100% and despite the slightly derogatory comments above, and I am aware of the limitations and issues with MFT, the benefits still do sometimes easily outweigh the negatives for me so I think I'll try and forget the X100x for now