White Scars and Allies

I've been considering what could be the best ally combination for White Scars.

I've considered generic Imperial Guard, as well as Elysians. The thinking was mostly the easy access to Vendettas and Hydras. In particular, Elysians have Valkyries as dedicated transports, which means you can have an 'air cavalry' themed army. Theoretically, this works well with White Scars, as it is an extremely mobile list.

I made half a dozen lists, involving Guard to varying degrees. However, I kept thinking that the White Scars were more of a token addition to the list. The truth is, Guard don't really need White Scars as allies. If you're taking a marine contingent to a Guard list, then you would probably do better to have terminators, death company, etc.

Instead, what I think may be a particularly good ally option is an Eldar jetbike contingent. Jetbikes move further than marine bikes, they ignore difficult terrain and the Farseer offers an inexpensive psychic defence. In addition, Eldar have both the Nightwing and the Phoenix, both of which have the vector dancer rule, which makes them more mobile and versatile to the Stormtalon. The Eldar flyers could quite quickly become a necessity, if Aeronautica becomes mainstream.

Here's the contingent for now:

Farseer w/ runes of witnessing/warding, jetbike, singing spear - 113
6 Guardian jetbikes w/ 2 cannons - 152
= 265 points

I may also take a second smaller squad, holding it in reserve to capture objectives late in the game.

The most characterful Eldar army for this kind of contingent is Saim Hann. This would go with White Scars in that they are both born in the saddle and have the similar 'wild rider' fluff.

However, I'm not a big fan of the red. I was considering starting a Mymeara army, modeled in Imperial Armour 11, as they are a stunning ethereal turquoise. I'm also considering using 'glacial' resin bases for my Scars, so this light blue would kind of match..

Now I just need to find a reason to explain why White Scars Legion, embarking on the Great Crusade, would take filthy xenos Eldar allies. It's not because I'm a beardy bastard, honestly.