Great minds, etc. I am working on exactly the same thing -- again. I
looked at it a bit last summer, but couldn't find anthing of
significance. Most equipment seems to be designed for commercial
(high-tonnage) applications, so it appears that the use of misters
may be the only alternative.

Last summer I found a system on-line that utilized RO water, but the
description was so poor I doubted the claims they made. The water
was applied directly to the condenser coils. RO water, like
distilled water, is slightly acidic, so I didn't like the idea of
applying directly to the aluminum coils. Also, they didn't describe
nor indicate even there was any special effort made to distribute the
water on the coils. It just seemed to be discharged from the end of a
tube onto the coils. I e-mailed questions to them but didn't hear
back.

As to your question, I don't have an answer, but scaling of the coil
is important to address. I'm considering a system where the
hard-water mist is discharged a few feet away from the AC and hoping
the mist all evaporates before the air enters the condenser. If that
occurs, then the dissolved solids might pass through as a dust. I'm
not terribly comfortable with this approach since prevailing winds,
etc., might drive it into the unit before evaporation can occur, so I
wondered about adding swamp cooler dismisters between the two.

Perhaps we could collaborate.

Where are you located geographically? I am in north-central Utah.