They don't need to save ID slots anymore when 1.7 mods come out sometime next year, with the new name ID system having been introduced in 1.7 and the old numeric ID system being phased out sometime in the future.
I believe that the new system is part of what JadedCat is working on along with the standardized configs for the new launcher. She was working on clearing duplicate block types during Slowpoke's twitch cast earlier in the week and a lot of those issues have to do with Ore Dictionary names.
At least I'm hoping FtB is trying to be that proactive.