The times and the markets are all a changing.  The big garden tubs with jets galore are going away, the same wayas the dodo.  

Modifications to air handlers make sense as the latest greatest but need more marketing efforts before they become mainstream.  

Life, not just real estate, in Southern California presents the opportunity to see all kinds of home features/upgrades.  How long will each be relevant?  People have different wants/needs.  "Meaningful" is yet another word where the definition varies.  

None of those have any market value nor have I encountered them in CA.

Annette, I like the way you share your unlimited thinking ... expanding t reach the possible needs of people today.  For the most part, my experience is that a majority of people (my opinion) are seeing the light about the pandemic induced virus. 

#1 - not really

#2 and #3 - these units have been around for some time (I put in #3 myself and love it) and they have been a good selling point if marketed correctly and buyers are being educated about the benefits. 

As the human body needs bacteria to survive I say NO!

I have no idea what long-term value such features would add. If the pandemic is long-term, they would make a difference. If not, I don't see them as being more desirable than new counter tops, flooring, paint, etc.

Absolutely none for me personally!

These are not priority concerns.

1 - no

2 - possible but not enough people know about it.

3 - same as #2, not enough people pay attention to that stuff.

Nope not in my area. Seems that everyone is getting into making their house ugly with solar panels all over the front of the house.

2 & 3 

I've used an air filtration unit in my home that uses a combination of  UV, Hepa, and NASA technology. If I had an air handler I would insist on 2 & 3 

1.  No.  Salons may be closed but there is an underground network out here and some outdoor salons exist.  Or if you're Nancy Pelosi, the rules don't apply to you and you go maskless indoors to one.

2.  This may become more common in commercial venues/sporting halls/beer halls/etc.  Read a good article about this from an economist I follow about UVC light and a safer way to implement it.

3.  I can see that being something that is useful even w/o the Wuhan virus in play.  Now that smog is back in So Cal and we have had hazy skies from the state's brush fires for weeks now, it could be useful.  Personally, I pay the $20 for the top of the line filter for my AC that gets the pollen, dander and most viruses.  Have for 8+ years now.

I have not heard of any of these being advertised selling features out here (or at all).  I'm sure realtor magazine will jump on the bandwagon though soon.

None of the above but those items are so specific they will probably appeal only to certain people and may actually turn some buyers away. 

I haven't encountered any of these here. (Montana)

I would think it would be a negative to the value.