Yes, I've discovered it's not only possible but relatively easy, to thicken fiber reactive dyes and use them for printing.
In my continuing effort to step away from the computer and get my hands more directly into my work, I've been trying some different methods of printing on cloth. After researching methods, I did a bit of mad-scientist style blending of dyes with various mordants and thickeners and used a brayer to quickly lay down some stripes.
detail of 2 color fiber reactive dye thickened and applied to cotton with a brayer
There are some interesting details within the piece. Think I'll do some hand-stitching and work on a cushion.