If you want to go to the hassle of swapping rather than buying a 1.5, go with the 1.8. 4A and 7A - I don't know how easily they'd be mounted in your car. But as for the NZ, the 1.3 and 1.8 both come in the corolla, so should be similar.
Brakes are not the only thing you will need to replace. You'll have to replace the dampers, springs, swap bars, probably have to add strut bars both front and rear to add structural rigidity and reduce body flex. Will have to put bigger tires and maybe 6 inch wide wheels, more if possible.
The good thing about the vitz is that TRD makes a lot of parts for it, so a lot can be done fairly easily.
Best of luck.