So, here's the problem with non-boa haste stacking: The best haste weapon in the game right now, beside boa maces is the caster Dagger from BFD, that gives like 5 haste.
Issue? 5-10 damage. Daggers around that same level have like 18-35ish.
So, from what i noticed, lavalash deals 400% AP damage, which would go from your AP, and while low cooldowns would help having more lavalashes and flameshocks, you would be doing next to no damage in whitehits.
I was considering stacking Agility/AP, with some haste on cloaks, trinks and robe chest, and going Wicked Daggers for more whitehit pressure.
What do you think?
Now, I'm no theorycrafting expert, but I very much enjoy putting pen to paper and figuring up dps scenarios with different gear options. Your idea is worth exploring at least as an exercise. However, a few things get tricky when theorycrafting PVP gear. A certain stat might help you in one specific encounter, and be horrible most of the rest of the time. If you want to run the numbers as best you can, you might get some hard theoretical results. In the end though, I generally turn to just trying out gear options when answers get fuzzy.
You can of course run several battlegrounds, duel, etc and see what at least appears to work better most of the time. I also regularly test straight dps on WC trash and bosses by myself with the different gear options, analyzing things with an addon like recount. The issue here is that oftentimes PVP isn't about constant dps, but rather burst damage. Really I think it boils down to playing games and getting a feel for what works better. If for instance you have people getting killed just before your heal lands, try some more haste. If you find you're getting burst down in seconds, you might try more stamina. If you consistently land heals on yourself, but continue to fall behind in keeping up with the damage, shoot for bigger heals. The same works in reverse for making decisions on gearing for damage.
I hope this wasn't too much of a big bummer of an answer to a fairly straightforward question. I'd really like to know what you settle on. I was messing around with the type of setup you are talking about (minus the Wicked Daggers) today. I used 2 McGowans, 1 haste trinket, haste belt, Foreman's Gloves, and DPR which got me to 8.32% haste. Cooldown on LL was 9.69 seconds. Attack speed down to 2.59 seconds. All this out of battlegrounds. In trying this against going straight agility and reasonable crit, the agi and crit set had fairly consistently higher numbers. But..... Healing Surges were down to 1.38 seconds and of course LL would be ready .71 seconds earlier than without stacking haste beyond the McGowans. There can be some value in that in a PVP setting for sure, so I dunno.
I know, I said a whole lot only to really say nothing, hehe. You can see why it takes me a long time to do anything. You seem like you are on top of things. If you have the time, I'd try and get the gear you are talking about an give it a go. I'll give it a shot as well as I have time.
One thing to specifically keep in mind is that if you plan on off-healing and purging any decent amount (and I personally would, given enhance's relatively low damage with any gear) your white damage will be on hold while casting HS and Purges. If you want to just keep it to straight ahead dps, I would really test out options pretty thoroughly on elite mobs. Recount, or some other addon, will tell you what kind of results you are really getting in white hits and how much that counts in the grand scheme of things.
Nice artwork btw!