leaving a MEP to be standalone plan

We have a potential new client that is unhappy with the MEP that they joined 1/1/23. They would like to leave and become a standalone plan. How does a plan leave a MEP and become a standalone plan? Is this possible to do mid-year?  

Would need more facts, but generally there is the ability to tell MEP to spin off the part of the MEP for that employer into its own plan sponsored only by employer.

I have received a copy of their plan document and it looks like they need to give 30 days notice to the lead employer of their intention to withdraw from the MEP and they are free to establish a spin off plan. Are there any issues doing this mid-year? Can the spin off plan have a 1/1/24 effective date with deferrals starting  7/1/24? How are the two partial years handled for 5500 purposes?