Can this be modified for freezer prep?

I guess you're wanting to save extra chicken or prep time when you defrost a meal in future or both.
There are options.
For safety, if the chicken was sold refrigerated and stored either just two days or to store's best buy date, it's better to cook before freezing.
Stored long beyond the two days or best before label- iffy.
Also I think the taste will be better if you saute before freezing.
Last, if it's still within the safe time range, raw chicken stores longer in the freezer than chicken casserole (roughly a year versus three months).
Your choice.