Well, that sucks. Then I would have to use a core mod? I'm not too knowlegeable on core modding other than it is advised to use a different apporach and 99% of the time there is some better way. Would a purely additive core mod, a mod that only adds fields and classes, still cause issues with other mods?
Also, is there a way to change the class of a minecraft block without registering an entirely new block? If I could simply make a subclass of a block's existing class, I could register the block as being a part of the new sub-class which would contain functionality for what I want to do. This would, of course, only apply the functionality to blocks that I make a new sub-class for.