Dude you have to tell me your source for inner knowledge of Games workshop! We need to get more updates on rumors man!!!
Where and when did they say this? It has been said by FW that they did intend to have it played with people's existing armies as well as new ones.
It kinda says it on Pg. 148 of the Horus Heresy Book one. "The armies for these games should be taken from the Space Marine Legion Crusade army list, and then later, "they are intended to be used with the Age of Darkness army selection rules." It then goes on to specifify custom missions, warlord traits and all that.
I mean, they're fairly clear that this is an entirely separate game, mostly using 40k rules but apart from it, like apocalypse. And these units aren't even part of any of the standard codexes! It is it's own, entire codex unto itself! Everything else from forge world fits nicely in the Tau codex, or Orks, or whatever. Or maybe something like Death Corps of Krieg that is really just a reorg of IG.
Again, it's really super clear these units are not meant to be played with "normal" 40k. You can't even use normal 40 k units with these guys when playing a Horus Heresy game. You have to use a Legion Tactical Squad, instead of something normal.
Eh, whatever. I do not care enough to make as big a deal about it as it has apparently become. You are right that probably is not all that unbalancing, at least if you can't bring Primarch's et all. But it is quite silly, even nonsensical.
Normal foregeworld, I have no problem with, especially when we aren't trying to be serious. I have quite a bit of FW Tau myself. But HH is not for normal play any more than super-heavies, titans and strategic assets are.
