It's going to take up more space than 3 other aircraft at the terminal for a start.
Then you also have the cost to upgrade domestic terminals.
Then you also have the problem that business pax want frequency as well as on time departure.
One A380 every 90 minutes or more will not cut it with them.
I could be wrong but I also think you'll find it will probably be only be fuel efficient on long flights not short hops like the golden triangle.Then it will also be only viable if it is full and not very early or late at night so it's utilisation will be less as a domestic aircraft.
Not a good idea