Good (Not Dark Eldar) Ally for Eldar

I have enough models for my Eldar army that I am looking to possibly start another one. To that end, I would like to collect something that does OK as an Eldar ally with the new rules. I am not interested in anything cheesy, but would like something with a little synergy. And I do not like Dark Eldar (fluffy reasons).

I love the new Space Wolf models, but I do not know how that would work out (and of course won't know until after the codex drops).

I don't care if it is wacky, but I do care that I have fun playing it and my opponent has a good time on the other side.

Thanks!

You have a Problem with DE for Fluff reasons but everything else is ok? Oo

DE are too evilish... (I know it's the grimdark and there are no good guys, but there are less bad guys :P) I probably wouldn't like Chaos/Daemons either, but other than that I am pretty open.

Actually there are tons of fluff out there which explains a lot of their relationship.
All others are problematic. Necrons? Nope. Chaos? Nope. Space Marines? Maybe... if you find a very very tolerant chapter or a very very dire situation. Tau? Maybe but this wont be any fun for your opponents. Imperial Guard? Maybe better than Space Marines and an Inquisitor could help. Sisters? Never! Orks? Nope.
Doesnt leave much space for potential allies.

Actually, Orks are quite a good one, because it represents them being used an manipulated by the Eldar for their own ends. Orks being fairly easy to manipulate short term (at least the Eldar would think it was easy... until it bites them in the ***. A squig bite). The Fluff being the Eldar force need expendable manpower to hold up a foe too numerically large for their force, and the orks are promised some cool dakka for their efforts (and a blade in the back after the battle is over).
For most fluffy allies, an Inquisitorial detachment led by radical Ordo Xenos Inquisitors is probably the best fit. Put some Jokaero in to show xenos tolerance and stuff.

Mebbe some Tau? Those space Smurfs are pretty upbeat and not at all Grimdark.

Eldar are the best army in the game in terms of pure shooting and the ability to grab objectives T5-7. Their only real weakness is that their firepower is least efficient against AV14, so they tend to rely on their Wraithknights in that case. You'd have to tailor your list specifically for heavy armor, which would weaken the list overall otherwise. They also aren't good at grabbing objectives midgame. They're easily fast enough to do it, but Eldar are fairly fragile so if you throw your units out there, they die. You might get a few Malestorm points, but you'll lose the game overall.

Conveniently, Space Marines are now the best army in the game for holding objectives early, and destroying heavy armor efficiently. Grav Guns, Meltaguns, Drop Pods, Biikes, and Rhinos give you a lot of flexibility in that regard. Take a Bike squad, a Chapter Master, a few Drop Pods, and back it up with Wraithknights and Wave Serpents, and you have an extremely competitive army.