I like the idea. I play mono stompy and I have a few suggestions.
1. Cut
walking ballista completely. its a stale draw early game.
2. add 4x experiment ones. This as amazing 1 drop, get better every creature and synergize well with Rampaging elephant.
3. 1-2 Rhonas. 4 is too many. Doesn't ramp the beat down early game.
4. if you are running such low cmc creature consider 4x
Collected company.
5. cut ghalta or keep one. to easy to counter or remove.
6. need at least one
scavenging ooze for graveyard hate.
7.
rancor difficult to pass up, but with the creature you have you might want to consider enter the battlefield efftects (especailly becuase of elephant)
8. With the the high mana cards
gone you can run 20 lands