I'm not sure I'm looking at this right. We have *very* hard water - scaling on pool tiles, shower walls, etc... We don't have the designated pipes in our garage for water softeners, but I'm thinking I would rather have it outside off the main line so the pool's auto filler will use the soften tiles. I'd put a water filter in the kitchen for the faucet and the ice maker. Is it a problem to put one off the main water line?
No it would not be a problem. Everything in the house would be soft.
I don't know about you, but even with a carbon water filter I do not like the taste of soft water. If you have an RO then it should be soft.
The other issue you have is the automatic pool filler; I don't know how much make up water that it adds at one time, but not sure the softener would be able to keep up with it. If it doesn't keep up all the water will be hard.
You could branch off before the before the softener and run lines to your pool and for drinking water.
"Clarity to Agreement" Dennis Prager