How to set up HSA default during Loss of Eligibility Life Event (dependent ages out)

During open enrollment this fiscal year starting on 7/1/23, the Health Savings Account was introduced with two options: Self and Family.

We are now trying to set up a default enrollment formula for medical, dental, and vision plan types for the Loss of Eligibility life event. But because the HSA options are based on dependents or no dependents in the HDHP plan, we are also trying to set up a default formula for the HSA enrollment. The problem is if the employee loses electability into the Family option for HSA and needs to be defaulted into the Self option, there is no way to assign the coverage amount.