Well, i can tell you what im doing now.
First of all, as we have Wych Cult Theme Army we must have Arena's themed units.
1) Wyches (surprise)
Well, naturally Succubi and Lelith.
First of all, i know its a little counter-inuitive but i really think thats a starting point of a good Wych Cult army is a unit of Beastmasters.
Wyches are fragile, really fragile, first and foremost you need bullet spounge. Wyches are all classy, high caste, masters of performance and bloody bath. They dont open the battle, they join in to make it spectacle. So they need something to open battle for them.
Beastmasters are excelent at this, and they also very cheap (points wise, only pointswise).
Most of the time they can assault at turn 2, and also they cant be ignored, cause they will wreck face if they will will be ignored.
We are talking about unit 4 Beastmasters 5 Khymera 6 Razorwings Flock, 39 wounds unit.
Or 4 Beastmaster 8 Khymera 4 Razorwing Flock. 2 variants one have more Khymeras with their 4++, another more wounds and deadlies atack.
Now, actually wyches.
In my opinion there are 2 primary ways of running wyches now.
1) In a raider, 9 strong with Succubi. This unit is primarily wounds and blades for Succubi. Without her, they are largely toothless. But can wreck any tank naturally. You should know about haywire if you want to collect Wych Cult army, i wont stop there.
Dont hesitate to place this Raider is reserve if you know it will be the target, if you go second. For that reason my Raiders with Wyches have Enhanced Aethersails upgrade.
2) In a venom, without any upgrades, except haywire. This unit is a support unit. It must join other units to be effective. It can eat tank, it can throw plasma grenade, it can sit and go to ground at the objective at later starges of the game. Point of remedy of such a unit is Venom and Haywire Grenades.
You need to decide how many and on what platforms will your Wyches go at that point.
They are basically T4 Wyches on a bike that can slice heads. I really think that Reavers fit in Wych Cult army very good, primarily because they are very tough and because they have that beautifull option to have Heat Lance. Also because they can charge something and hold it at place, while girls are going. Or beasts. Or Talos. Or whatever.
Find guide on this site, by Mushkilla about Reavers.
Im building 2 units of 18 for my 1.5 Wych Cult list.
They bring reliable AV on the table, that wont be killed in a matter of seconds. If you dont take Reavers you probably will need to think how will you cover your ranged AV at that point.
Bloodbrides. That is touchy subject. Girls themself are nothing to speak of, for their price. But they suddenly come in a small groups of 3 and can take very and very powerfull squad leader - Syren. She is even worthy of an Agoniser. I would stay away from big units. They seems okay to be in reserved raiders or venoms, with some killy HQ and Grisly Trophy upgrade.
Appear and wreck face.
There is also a big temptation to create a big unit full of Wych Weapons and some mega kill Succubi or Lelith. Dont go that way. Other units can do it better and cheaper. Like beastmasters.
You dont really have to take them, but they are a nice addition. They are also the way how you can incude Lelith in your list.
Well, you can take anything you like.
Ravager, or Razorwing Jetfighter.
Or even Talos, i know he is not fluffy for Wych Cult, but it is just incrediblle how survivable your wyches will became if you will have it in list.
You can forgo Heavy Support altogether and take more Troops, if you have AV covered.
Weapons of Wych Cult.
In 6th edition weapon of choice amongst Wych Cults are Venom Blades. All of your Hekatrix, Arena Champions and probably succubi should have that weapon. It is excelent and very cheap.
Sadly agonisers are now just not worth their points.
Another weapon i really like on succubi is a Power Spear. It is basically an agoniser for one turn for 10 less points. And if you play right - that one turn is all you need. After that you have venom blade.
All of the Wych Weapons are not worth their cost in my opinion. Thats 10 points better spent elsewhere.
You should always equip Haywire Grenades on anything that can take it, that is your primary AV tool and frankly, reason why Wych Cult can be playable at all.
Oh, and dont give Beastmasters any upgrade, ever. 1 atack max, not worth it.