Actually George, I have a very good idea. You keep talking about it. I also deal with folks in a wide variety of climates, from arid to extremely humid, beyond Indiana.
A good approach would be to examine where your excess humidity comes from. Is it air changes bringing in outside humidity? You know what happens to rh when you bring hot air to a cooler environment. Is it water put into the air by your house and/or occupants? Take a look at the source(s) and you may be surprised.
We agree, dehumidification is critical, ac can be and often is used for that. The cost is always higher than simple dehumidification. With both, it only makes sense to examine the need and try to reduce it. Depending on your house configuration, you might find ROI on a heat pump water heater very short. Combination units (with tank) are widely available. I fault the manufacturers for not stressing that free byproduct (cool dry air) we find so beneficial.
We accomplish a total air change every 2 hours. I bring in dehumidified air this time of year. My house is slightly pressurized, air leaks go out. We're also careful about adding humidity from the way we live here. Our house doesn't add any water to the air, but that is a common problem.
You're confusing your elderly acquaintance's problems with lack of dehumidification. Controlling the temperature with ac is not the same.
Go one step farther George, consider how an even better designed building doesn't need air conditioning. There's one in Indiana, Chicago area. Another project waiting for an excavator SE of Terre Haute. As everywhere humid, controlling rh inside is a necessity. An Atlanta house got an interesting combination of systems, but no ac needed or bought.
We go for simpler, maintenance-free (if possible) systems with low upfront cost. Makes for easy living. No worries about a failed condensate pump for instance, if there is none.
The Oklahomans (Tulsa and Norman) found that attractive, almost as much as a house that won't blow away in a tornado.
OK, I'm off my soap box now. Time to get back to my cheap effort to salvage these heat pump water heaters.