Only Caelum has Mammoths don't they? So strip Caelum of them and no mammoths...
Do you want to make the mammoth extinct, have you never watched ice age, how could you make them extinct again...
Rocks, rocks?!?!? Come on guys, how could they fly carrying a load of heavy rocks!?!? They use ice lances/ice blades because they are lighter then steel/iron presumably.
Personally if its not broken don't fix it and isn't Caelum ok as is?
Although alot of people seem to want to improve the caelum flying infantry which would be good but as already been said the problem lies with flying/fatigue. They fly in, lose formation and become easy targets. Its the losing formation and being open to multiple attacks that makes them weak. Not there stats.