is it actually possible to use the Keypad to open a door that uses the Nuki Box?
If not, would it be a suitable workaround to integrate the Nuki Opener within the Intercom, connect it to a Bridge and use the Keypad to open the door?
Yes, that could be a viable option, if you have Wifi and power supply for the Bridge in range. And you also have to keep in mind that the Keypad needs to be in Bluetooth range of the Opener!