I have to agree with sj113 here, it is a rather expensive steel-intensive unit if you take in all of the required upgrades into account. It has to give at least some benefits for it all to be even remotely worth the cost. Otherwise it will be the Seleucid Elephant Champion situation all over again, which seem to have been nerfed to oblivion, making them unsuitable for anything (in this state they can not be used neither to destroy buildings nor kill units). Just my two cents.