I say yes, but it's probably unfeasable without a reset because of how it's coded as EIRRMODy likely will tell you. With the forthgoing changes and perhaps the poor player choices your reinforcement package often turns obsolete. If you pay the standard 30 PPs to change I think you've earned it. Forcing players to delete previous reinf units might be an option too as prerequisite to changing.
Lai is correct.
To prevent abuse, if you changed your Reinforcement - youd need to remove all units from the previous choice.