The problem is not that it cannot be done. The automatic transmission can be attached to the engine very easily, and if the transmission is good, it would also work pretty well!
But my advice to you is not to go for it with the new model of corolla. In pakistan, the cars get spoiled as the as soon as the mechanics get their hands onto them. They cannot even put those things back together which they have taken apart in the first place, and working with proper tools (e.g. torque wrenches, and generally the things which affect the feel and longevity of the vehicle) is a different matter altogether.
The things required for the completion of this job would be:
To take the engine out (even worse, try to change the gearbox by leaving the engine inside, thereby scratching the new chassis)
They would have to alter the axle lengths and who knows if they balance them accordingly or not!?
Engine mounts could also be slightly damaged!
They would have to get rid of the clutch system and install a new brake pedal. How neatly this would be done is a question mark!
Electrical wiring would also have to be altered. In the original automatic, you cannot get the gearbox out of the P position without first stepping on the brake, and such fine issues!
You must keep in mind that this engine is not currently been marketed anywhere else in the world, just some other African countries with conditions similar to that in Pakistan. So your gearbox would certainly not be from a newer engine!
So my advice would be to do such a thing either with the 2000 corolla, as all the parts are readily available, or to buy an original automatic in the fist place.