How to field some odd beasts

I love these two models so I plan to add them to my collection (when I get round to it).

Although I think of myself as a modeller first, it is always nice to get minis on the table after putting in the time and effort to paint them.  I don't play WHFB, but I think these models easily fit the fluff as large beasts captured for the arena (I am planning to make the dragon without its rider).  So the question is, what rules do I use for them?  Here are my ideas so far...

CWE allies
The dragon counts as a Wraithknight.  It would be fairly mobile, but unable to fly properly (perhaps its wings were clipped).  Whichever weapons I costed for could be the effect of its breath (sadly no templates).  If I used the Iyanden rules, it could even by my HQ (I think - don't own the book yet), so I wouldn't have to take a random Farseer to explain away.  I can't see anything on the list which could obviously be the Kharibdyss though.  Perhaps my opponents would let me use it is as 5 wraithguard (troops in Iyanden list?) - ie. Wraithguard stats with 5 wounds and 5 weapons (decreasing as it gets injured) - I'm thinking d-scythes to represent some sort of noxious breath.
The big advantage of this setup is the fact that the beasts would be battle brothers.

Chaos Space Marine allies
The dragon is obviously a Heldrake with Baleflamer.  Sure, it has to use vehicle rules, but it now flies, vector strikes and breathes fire - I can't think of anything else in 40k with rules closer to a dragon.  The Kharybdiss counts as a maulerfiend (or perhaps a Defiler with cc weapons?).  The use of vehicle rules isn't a real problem as penetrating hits etc are just vital organs.  Exploding is a bit unusual, but there are plenty of weird beasts in the galaxy.
Problem is they would be desperate allies.  This could be explained for the beasts by just saying that they are really vicious, and not tamed, so they have to be watched.  Thing is, I would also have to take a CSM HQ and troop choice which would have the same issue, and need explaining.

Chaos Daemon allies
The dragon could be a winged daemon prince, making it a flying monstrous creature (and what else would a 40k dragon be?).  The Kharybdiss could be some other type of greater daemon.  The problem is, they would now be subject to the Warp Storm rules, as would the rest of my army.  And I would have the same problems of desperate allies and requiring an additional troop choice.

Tyrannid allies
Clearly the first hurdle is that no-one can take tyrannid allies, so I would need opponent agreement.  The dragon could be a Flyrant, achieving my aim of using him as a Flying Monstrous Creature again.  I don't know what the Kharibdyss would be - perhaps a Carnifex.  If I did this, I would need some troops once again, but on the beast theme, they could just be captured Tyrannid creatures used in the arena or in battle. If the troops were termagants, I could even count the Kharybdiss as a (funny looking) tervigon.

So what do peole think?  Do any of the ideas have mileage?  Does anyone have any better ways I could use these models with my Dark Eldar?

I like the cut of your jib, and I like the helldrake/carnie rules as proxy. Alternatively though, why not just make your own rules and organise an arena-type tournament?

I just thought a great idea for a scenario, or perhaps just some really good photos...
Build an arena, put a lot of wyches, beasts and these two in.
Then a great cinematic shot from it, would be awesome!

Seriously, wyches against a dragon. I want to see that!

In my Skaven-counts-as-Tyranids army, I have this model as my Harpy, with a Grey Seer riding it. It's a lovely model.

I love the idea of it as a Wraithknight: it's a fracking dragon, of course it's tough! Plenty of modern depictions of dragons have them spitting ranged fireballs rather than spurts of flame, so that works.

The modelling ideas are huge: I wouldn't even be offended by using it as a Talos; certainly even if you used the Wraithknight rules, it could be a Haemy's pet construct; kitbash flails to its claws, ichor injectors on its back, ribbed pipes for feet etc.

Just to clarify - Warp Storm rules are never in effect for Daemon allies, only Daemon primary.

I also just picked up one of the Kharybdiss which I'll be using as a Soulgrinder for my Slaanesh army, and the fun DE Beastmasters probably as...Beastmasters, just stick them on helboards

You could always go with the Dragon as a Prince, the Kharybdiss as a Grinder (which, with anti-air shooting isn't too shabby for a DE list, neither is the FMC) then just take a unit of Wyches and run them as 'counts as' Daemonettes. Fleet, assault oriented, rending, hard to hit - sounds like Wyches to me (you could even build them out of Fantasy DE and then their lack of splinter pistols is modeled in and also it will make them easily distinguishable from any regular wyches you're fielding)


I could also, honestly, see running the dragon as a 'counts as' Razorwing or Voidraven and the Kharybdiss as a 'counts as' Talos.