Personally, while it may not be as fluffy, I think a wych cult list is better served by Duke Sliscus rather than a Succubus and Haemy. Giving all of your dedicated transports deep strike, and allowing you an extra roll on the combat drugs table for all your wyches is pretty awesome, and he's no slouch in CC either.
I've personally toyed with the idea of fielding a massive number of wyches, and what I've found is that if you're going to upgrade a unit to do well in CC offensively(ie, with a power weapon/agonizer), it works better if it's a unit of bloodbrides. Having 3 shardnets + the offensive syren in a 9 wych unit tarpits things like crazy while your syren goes to work doing the killing.
I'd keep your other 5-man wych units as you have them, just with the basic HWGs. At 1500 points, you could field:
5x Haywyches w/ HWGs in dual cannon venoms
1x 10-man warrior squad w/ SC and 3+ poison shots in a decked out raider(dissies, flicker, grisly trophies, splinter racks)
9 Bloodbrides fully decked out with syren, pgl, agonizer in a fully decked out raider(dissies, flicker, grisly trophies)
1 Voidraven bomber
1 Ravager w/ flickerfield
That's 12 units with "objective secured", plenty of haywire/AT, tarpits for days, and 9 vehicles at exactly 1500 points.