Highlighted weapons are free options.
Support Sangonomiya Kokomi focuses on just using her Burst before her Skill's duration ends to refresh her Skill duration. This allows 100% uptime on Hydro application from her Skill for Freeze / Electro-Charged teams.
Sangonomiya Kokomi's Burst dynamically alters her Skill's damage, this means that you cannot use her Burst to snapshot the buff onto the Skill and swap out.
Main Stats are not important for (4) if you do not need the extra healing. Focus on Energy Recharge substats instead.