I have a suggestion for a future release that might help with the offset issue if your code base would allow it. You could make all item ids for default game be negative and custom ids be positive. We did this in an application once to make it so we did not have to increment an offset every once in a while and then make all the custom items have to fix theirs. It would completely eliminate this issue happening ever again. Just a thought.
It wont happen anymore anyway, there is no posibility to increase the Ids again, Neither needed, about a year or 3 ago (or even longer) we added the ModApi.Application.GetBlockAndItemMapping() with this you automaticly get the right id and do not have to add any offset in your code
