Damn, you casually raising Den Ri Mi's death flag.
If Heki joins the HSU, which I think is possible after this arc, then Shin will get some mountain soldiers that way.
They're a good pair, and he'd be a great second option to Kyou Kai. More importantly, someone Shin could trust to hold have his back by holding the line at his flank.
My ideal formation for the HSU has Ka Ryo Ten on the vanguard, Shin in the centre, and Kyou Kai on one of the wings.
Right now, I can think of only two candidates that could fill that spot: Heki or Roku O Mi.
If Hara intends for Heki to remain on his own path to becoming a "regular" GG, then I can see ROM fit. The HSU would be incredibly tough to deal with.