recommendations for heating system

Hi,

I am in the process of remodeling a home in Palo Alto California (SF Bay Area) with the following characteristics:
-4000 SF
-existing forced air system for heat
-uninsulated slab on grade
-8 FT ceilings
-old 1960s copper-in-concrete hydronic floor heating system in-slab for first floor and in 1.75 inches of concrete for second floor (system was disconnected in the 90s and replaced with forced air)
-2 stories

I would like to:
-add cooling
-possibly improve heating system for greater comfort
-add warm floors to two full bathrooms (could be hydronic or electric resistance)

Because the ceilings are only 8 feet on the first floor, I've been advised that I shouldn't install radiant floors on the first floor because I'll lose some precious ceiling height. However, I've been told that I should consider installing it on the second floor, because the existing 1.75 inches of copper+concrete could be demo'ed and the height could be recovered.

What advice do folks have for me? What should I install?

Keep in mind that my California climate is fairly mild.

Is a hydronic system worth the cost?
Is it reasonable to install radiant floors on the second floor and not on the first floor?
Are there other things I should be considering such as hydronic ceilings on the first floor?

Thanks!!