I made some edits, reworded the custom jutsu and added more to the story, though I'm a bit unsure, I didn't want to, y'know, 'play the red sages' in a way, so I purposely avoided pointing directly how he joined them and kept it vague (also because I have no idea of how to do it, hehe)
I only included this jutsu because of the fact it's somewhat bread 'n' butter for Iwagakure nin in general (at least, it was). I wouldn't mind it not being used unless we're in cave, because baby, once in a cave it'd be shooooowtime.
I've added another B jutsu though, just to give him more destructive power.
Doton - Iwayado Kuzushi
Only really useful in a cave, it's not that useful but it's a cool technique. Maybe you should make this into a custom adapted technique that is the same, except it is also possible to create small earth slides with this and cave in the ground beneath a battlefield, it might be more useful. Cause I don't know how much caves we'll be visiting.
I only included this jutsu because of the fact it's somewhat bread 'n' butter for Iwagakure nin in general (at least, it was). I wouldn't mind it not being used unless we're in cave, because baby, once in a cave it'd be shooooowtime.
I've added another B jutsu though, just to give him more destructive power.