The pack is nowhere near complete with the beta release, it was to test the launcher, nothing else... (might be third time I type that in two days...)
As far as I know, you are always better off adapting the ID manually, as the pack is designed to have its mods have their specific ids so you can easily join servers without trouble.
So if you want tto add mods once the real pack is out, just put the new id where there is nothing, and don't use something that might override the existing ones.
Plus, ID resolver has always been a little buggy to begin with.