What are the challenges in combining the two different plans?

Summary:

We have a requirement where we need to combine two plans and make it one, but the eligibility is totally different

A plan
employee is eligible if Hiring date on or before December 31, 2023
B Plan
Employees with less than 1 year of service duration will receive pro-rated incentive provided their date of joining is on or before September 30, 2024 .

And also, B plan includes proration while the other does not and also is there any challenge if we shift from UI to redwood.

What can be the possible challenges?

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