Can you tell me the potential of a heat pump? How warm can I get the water temp? I was told a heat pump on;y gets the water so warm, and that you still wont be able to swim for a few months?The cost for the heater is not dependent on the size of your pool. $5K is probably about right if the heater is a 140K unit. The Hayward 144K unit is near $4,000 on it's own, so the extra $1K would be for electrical and installation. You can save a few hundred dollars on a smaller heater... but long term, the heater will be less efficient, and will work harder and take longer to get the pool up to temp. I always recommend getting the biggest heat pump you can get.
You can add automation later, but it will cost you more. It's much easier to wire everything for automation at the start. If you add later, they have to wire for manual use now, then will have to rewire everything later for automation.
After 3 pools, I would never put in another one without automation - it just makes everything much easier to run and schedule.
I would definitely add the heater now - if you don't, you probably won't be using the pool in January - March.