Supersedence rule that does not remove the superseded application

Hi,

I am upgrading app1 with app2. I only want app2 to apply to devices that do not have app1 installed (rebuilt or new devices etc.)

app1 is currently deployed to a collection which is queried against a whole model type of devices (approx. 1000 devices) and I would also like to do the same with app2.

How can I use supersedence in this case?

I thought within app2, I could add in app1, but leave the 'do not replace' function selected, so it knows it's superseding app1 but it will not replace it, but when setting 'do not replace', the supersedence rule disappears.

Due to the importance on this application and the amount of devices it is assigned to, you can imagine my reluctance to get this wrong.

Any ideas??