6th Edition has dropped and the nonsense has begun. SandWyrm over at the Back 40k already came up with combinations of allies that are broken. This is before the rules have even been read. Why would you even do this? I seems like SandWrym is trying to point out what a super-bad idea this is by point out how you can abuse the rules to make the game not fun anymore and that is a good point. Unfortunately, it is impossible to make these combinations before you even know how they are made.
In the video, they never talk about more than a single unit of an allied force. They also never mention if psychic powers can affect allied units. SandWyrm made both of these assumptions.
I think that they are opening a big can of worms here and if they do not approach it carefully, the fallout could be immense. GW has had a poor track record of thinking through new and exciting things and ending up having to do some serious backpedaling with FAQs. I think that they are running the risk of doing this with allies.
While this is a risky call in terms of rules, this could not be a better idea in terms of generating revenue. One of the biggest limiting factors for GW's structure is that an Ork player is typically restricted to collecting only models in the Ork range unless he decides to start a new army. This opens up the whole GW range to any collector. Now they can sell the Ork player CSM and the CSM player Tyranids.
While awesome, this is going to get silly fast. I am a little scared to see how people are going to abuse these rules for power-gaming while giving half-assed justifications or no fluffy justifications at all. SandWyrm's post is a prime example of this. The rules ain't even out yet and they are building super units.
With a lot of these new rules, it seems that in retrospect that Apocalypse was 40k 5.5. I'm seeing a lot of half-formed rules in Apoc that are now more fleshed out in 6th.
We're living in a brave new world, boys and girls.