It is hard for me to say if they would do well together. My pen is big enough that several different critters can survive together. All bets are off on the babies though !! Granites get nice sized and are very skittish( from what I have heard!!!) so they might do like the Blues I used to keep in the pen. They crapped out when put in smaller tanks. Now--would they fight over a cricket--- heck yes!! I got a pic of a DI, crevice spiney & Yarrow spiney jumping on one cricket. A full grown Granite might not back down to a DI. Ther could alaso be problems with the temps--- I'm not sure of that either.
Just some thoughts ( how about a nice young Chi-wa-wan striped whiptail????--an all girl species)