Expand the kitchen, move the formal dining room to be next to the kitchen, expand the mother-in-law suite, add bathrooms to each bedroom so every bedroom is an en suite and have a half-bath (or maybe full bath) for guests. Large walk-in closets for all bedrooms.
Add an extra space to the existing 2 car garage.
Walk-in pantry for kitchen.
I need 1000 more square feet at least