Welcome to Macrossworld (and to collecting the toys)! And thanks for the interest in my set MG set.
The Minmay Guard set was designed specifically for a completely white 1S (i.e., stripped, primed, and repainted for customizing). The decals wouldn't work with either the Max or Miriya 1J. I made these particular designs semi-translucent so they'd blend into the white paint job REALLY well. As a result, if you try to put them on a darker surface the bluish purple wouldn't show up correctly (perhaps not at all). I can make an opaque set for you, but I am not sure how it would look against the paint schemes on the 1Js. My aesthetic gut instinct says it's not the best idea, although definitely a creative one.
If you're looking to trick out your 1/48s with some custom decals, drop me a PM with what you have in mind and I'll what I can do to help.