I have quite a few login items on my Mac, mostly Apps that I want to have idling in the background (like Tweetbot or Reeder), but that I don't use immediately. I would like to give these Apps an initial niceness of -20, since I care more about a snappy system start than Apps that I don't use right away (but still want to have started automatically with the system). However, after some time they should automatically be reniced to 0.
Is there any way to achieve this with login items? I know that you can give launch daemons an initial niceness (but you have to manually renice them). I suppose it's also possible to write a script that sets the niceness of some Apps to -20 on system launch, but I would prefer a cleaner ans easier to maintain way to achieve this.