It seems that you have already prejudged the issue to the extent that you feel that the senior personnel in your organization have ego issues etc. Instead of coming or rather jumping into conclusion why not have an open meeting with those who you think have such issue along with the management and try to explain the rationale behind making the new employees as Reporting Managers . Much of the bad blood can be stopped if one stops acting on assumptions than real issues, even if there is one.
Ego is not an issue but only an inflated ego is, try to be in their shoes and understand their concerns which is one of the areas of HR in any company and get to the solution even if it is not easy.
Thanks and Regards