dog,
The big problem with adding automation is not being able to connect things due to the decking.
A good example is a pool light. They have to be controlled by something. Either a switch, controller or automation. If you initially build the pool with a switch by the back door, and later install automation, you might not be able to run wires from the switch unless you dig up your new deck.
This type of problem will not be an issue if you plan for it.
I always recommend adding automation when you build the pool. It just makes the most sense. If you don't, you will have to add some kind of load center for all your pool equipment circuit breakers and then replace it with your automation system. In most cases the conduits and the wire length will not be the same.
Penny wise and pound foolish in my opinion.
Also.. Before an ounce of dirt is removed, you should decide exactly how you want your automation system to work. What is it you want it to do? Then your contractors can make sure that the plumbing, electrical and gas lines support how you want the pool to work
A very simple example: Let us say you have a waterfall and bubbler and want to be able to turn them on one at a time, or both at the same time, and controlled by automation. If they are plumbed using a single 3-way valve, (the normal way) it would manually work, but it would not work via automation. You need to know what you want before you start.
Thanks,
Jim R.