We are currently looking to buy a house and when we do of course I will have a RO system and be mixing my own water! No question about that...If you are in this long enough you will find that nobody makes perfect water for you. You can either pick a salt an live with it, or just figure out how to make it your own.
I figured out how to doctor up IO about 15 years ago and it only takes me a few seconds with some hardware-store materials to make it the way that I want it. It only takes one time with the math and hard work and then you just repeat.
Mixing salt in your own home automatically adjusts the pH. The co2 in your home will mostly determine the pH of your water, so when you mix it at home the mixing bin usually matches the tank unless one is in a room with vastly different co2.
You can buy an adapter to run a RO unit out of your kitchen or bath sink. Even a simple unit with a few stages is much better than tap water. A camping container with 7 to 10 gallons is easy to store and keep even in a small space.