Actually, in many aspects, that depends largely on plugin creators and distributors and not so much on K-M crew. For example, you cannot even download some plugins unless you have IE or Netscape. Some do not work with K-M (or Mozilla) at all or work poorly. Others are difficult to install with K-Meleon (or Mozilla) because they have not been created with K-Meleon in mind. It's all just another example of browser monopolies. So what we probably need here most of all is to make plugin creators support alternative browsers.
There is an easy way, though, to switch installed plugins on and off in K-Meleon.
The program is called Plugin Chooser and it works seamlessly with K-M. You can make a macro to run it from some menu in K-M. It disables and enables plugins on the run without the need to restart and also gives an overview of loaded plugins.
The program can be downloaded from
http://www.asahi-net.or.jp/~rb2t-kmc/soft/npc11a.zip