Have you looked into the high velocity, small diameter systems? The outlets are only a few inches in diameter and the velocity is high with a good difuser to distribute the air and prevent noise. The most outlets I've seen from a single ductless system is three. They can work well, but you do lose some wall space.
As to dehumidification...you need to be able to move air across a cold surface to condense moisture. There are some techniques that run air through a chemical absorbtion bed, but you're still moving air through it. On those systems, once the chemical has absorbed as much moisture as it can, you have to then open a vent to the outside and heat it up to force it to release the captured moisture, so it isn't necessarily all the efficient, and you don't get any of the benefits of cooling.
What some commercial units do is run both the heater and a/c simultaneously - the a/c to remove the moisture, and the heater to raiser the temperature, if the outlet temperature is too cold. That's rarely used in a residence.
For moisture control...the best thing is a properly sized a/c unit (i.e., the worst thing is one that is too big). A variable speed fan can really help, too, as it extracts more moisture on each pass if the air goes over the coils slower. You feel much more comfortable with dry air, than colder, damper air.