unfortunately until now no one found the time to reply to my question. i still would be curious.
anyhow. i finished my script to convert one effect to another. in my case i needed to switch the 3rd party FE-Toner to the built-in Tritone Effect. Except the fact that i can only copy none keyframed effects it works like a charm. At least on my system.
If anyone is interested in the script i could email it.