I'm think the same right now, as I only have one i40. Nearly bought a couple of i60's after borrowing on for a run and gun event launch I shot for Heineken. But since I liked shooting with the AD600 so much and the rumours of Fuji compatible flash fast approaching from Godox, Elimchrom and Profoto I though I'd just hold off a little.
A GN36 flash had little to offer me really but now that they have a GN60 speed light in Fuji, with TTL and HSS, I might go 'all in'.
I never took to the X1T though, I find it not so good to change settings with. Nissin's Air1 is really nice to use although I think now the camera menu can control things so perhaps it is a moot point.
Alan, I always found Nikon files to have a little too much green in them and Canon a little to much red, the later being much better for people to my eye. But as for documenting more close to life, the raw files are colourless and low contrasty from Canikon, if anything the raw files from Fuji are more close to real life out of the box.
I remember how amazed I was when I did my first shoot with Sigma art lenses on the 5D3, the colours and contrast in the raw files where so much stronger than any of the other Canon 'L' lenses I had, one can only guess that the lenses have much to do with how the output from the camera looks. Just because the files are rendered differently in your processing software doesn't mean there is something untoward going on, it just means it's different than what you are use to, if you shot with Fuji for 10 years and then Canon you'd be saying how flat the lifeless the 'digital files' look from the 5D. It's simply the point that you are looking at things from. Different processor design, different sensor design bound to give a different look.