Ahh... seeing your outside well stuff, I had figured you were in the part of FL without freezing worries. Maybe you could put a lift-off housing over the well. That would make it accessible for well work, but provide some insulation. It would also protect from the sun. Maybe even just adapt a car cover.
Yes, lack of space is a valid reason for a tankless. Others would include that you are using $0.40 per KWH electricity or propane for water heating. If electric, note that the tankless WH draws a lot of KW. So upping your electrical could be needed.
Similarly, cabinet softeners can be nice for space. They are not usually as repairable as the softeners with separate brine tank, they are space savers. Often they are treated as FRUs.
I would put a cartridge filter before the softener. You should also get a water test telling you iron as well as hardness. Do you have a sulfur smell? Maybe a wye screener at the well and a cartridge at the house.