I was ussing the Fujifilm inks for the Drylab printers for quite a while and imported expired 200ml cartridges from the U.S. several times over the years until the Epson ET7750 with the bottled Epson inks got onto the market - with the 114 inks with Claria like fading performance which made procurement of such inks much easier.
I tested as well the Ultrachrome D6 inks for the Surelab printers with similar performance, but these are more expensive.
I'm mixing the M and C inks into light inks for a L1800 - 2 parts dilutant and 1 part C or M, the L1800 does not use a gray ink.
I was mixing inks as well for the pigment ink printer P400 - the red as 1 part yellow and 2 parts M, and the orange with 2 parts yellow and 1 part M , and I'm mixing a gray for a Pro7600 with 1 part dilutant and 1 part black. I did as well 2 parts dilutant and 1 part black, both combinations do not cause problems with profiling. no impact or deformation of the gamut volume; I just use this 1:1 ratio which puts a little bit less ink onto the paper, I have one paper with a rather low ink limit - the 2:1 mix caused some ink puddles on the paper.
I think that the mix ratios 2:1 or 1.5 to 1 or similar are not that critical as long as you create specific icc profiles for the resp ink/paper combinations.