Have the tempad be activated in a dispenser and open a portal to a random location from the list

I’m planning on creating a device that allows you to create portals with a machine of some type.

Normally I’d agree but I have some other things I want the device to do, namely the size of the portal that the device summons next to it and for it to stay open for a prolonged period of time, with redstone control

that was my first idea, I just like reusing vanilla stuff when possible