Add Coverage in Medical Plans

Summary: we have a requirement from customer that for Marriage benefit Life Event if the employee has enrolled in any of the HSA or HDHP medical plans then they cannot drop their coverage but can change tiers. However, if they are on Waive in the previous enrollment, the Marriage Life Event should allow them to choose HSA or HDHP plans. with Change in Option not Plan it is not working for all scenarios. is there any way through configurations can we achieve this? or do we need to write FF? if so which FF and any sample code would help.