I think your current arrangement seems to work, if you can show that only changing your wifes residence will not affect her time with the kids or the schedule they are already on, I don't see that you'd have a problem.
You can show that the neighbor hood is not as safe and that the school is not as good. But I wouldn't hang my hat on that. It's worth noting, but not pursuing. It's better to pursue the benefits of the children remaining with you.
I think you may have an ideal solution. In the agreement stipulate that the parents have joint legal custody with joint physical custody with overnights as follows (60% dad/40% mom). Each parent is to support the child on their time. Dad is providing lodging for 52 of Mom's overnights and Dad will cover children's basic clothing, school fees and reasonable medical costs. No additional child support is ordered.
On 1st, 3rd and 5th weekends (defined by Friday's date) Mom takes the kids to her parents from Friday after school until Monday when she drops them off at school (keep them in the same school).
Every week, mom comes over after school on Wednesdays and stays overnight in the apartment and gets the girls off to school on Thursday mornings. You can sleep upstairs that night.
Holidays...mom gets every Presidents' Day, Columbus Day and Veterans Day from Sunday at 6pm until Tuesday when school starts.
Even years, mom gets (dad gets in odd years)
*Spring Break (from the time school ends until she returns the kids to school when it resumes)
*4th of July (from 9am on July 4th until you get off work on July 5th or Noon if you are not working)
*Thanksgiving (from 9am to 9pm)
*second half of Winter break, to start no earlier than Dec 26th at 9am and end with the kids return to school)
Odd years, mom gets (dad gets in even years)
*Labor Day weekend from Friday after school until Tuesdays return to school
*Memorial Day weekend from Friday after school until Tuesdays return to schol
*first half of Winter break, to include Dec 25th
All school holidays not previously addressed will belong to the parent with whom the children are schedule to be with that night.
Holiday time overrides regular parenting time and does not require make-up time.
Right of first refusal....any time that the child will be with a paid or non-relative caregiver (including step-parents) for more than 4 hours, shall first be offered to the other parent.