You mentioned switching them to an EWR departure and you to a DCA departure. You'd only be able to do that if the schedule change was on the outbound, not on the return. You will NOT get both the departure and the return cities changed to EWR, which is what I meant by "both ends." You have a decent chance of getting the return flight to route into EWR instead of PHL based on the "layover is much longer now and rather inconvenient as I will have to drive when I get there; the other destination is much better." But you won't get the start and end points both changed.

I hope that makes more sense.