I've seen the posts about occasional problems with condensation in the AMK PSK, so I was wondering if it would be a Bad Thing to pop a little desiccant pack into one? What about the AMK Mini FAK?

I don't see where it could hurt, other than taking up space you could put something useful in. I have 11 of the AMK/DR PSPs distributed between 4 BOBs, 4 GHBs, 2 Packs, and one training kit. All of the aforementioned kits but one are still stored in the original pouch, and none have had a condensation issue.

Might the space be better used for some Katadyn MP1 tabs?

If the AMK PSK/FAK container is not completely air tight, desiccant is of no help as to the damage that high humidity and rust can cause. My part of the country has extreme humidity and salt water breezes. After opening an airtight pack containing practically anything metal, I place a couple (depending on the size) desiccant packs in on closing, along with a humidity monitor strip.

Even though most anything steel (including stainless steel) rusts around here and fast, I’ve found a few exceptions in my rust fighting years: Victorinox knives and the proprietary finishes on Berettas, Glocks and HKs (although a few of the internal parts on all three will rust).

For what it's worth, here's the line of desiccants and humidity indicating cards I presently use:
http://www.desiccare.com/products.html

To determine the amount of desiccant needed for a particular area see the desiccant requirement
chart on Page 3 of the following brochure:
http://www.desiccare.com/images/PillwPakData.pdf

Keep in mind that no matter how bad things get, there is no nutritional value in the major types of desiccants.

It sounds like it's only a consideration in damp areas. I live in San Diego. "Damp" only occurs after it rains. I won't worry about it.

Thanks!