If you plan on running Analytic, why not just run Choice Specs instead? This way you can trick your item away to a physical pokemon and give it an item that won't even help, much like the extra speed would.
I like your Sigyliph idea, and if you really only plan to defend with him its perfect. But something I would like you to think about is running it instead with Life Orb and Charge Beam. Even with Charge Beam's mediocre power, it does have like a 50% chance to increase your Sp. Attack, which will not only boost your power by itself, but it will increase the modifier on your Stored Power even further than you plan to, along with a 30% increase, free of charge. While your plan just might be better, think about it.
I wrote that BEFORE I realized you had a Skarmory already, so you can ignore it.
Yeah, that sounds good. I find that Ground-types on the switch works pretty well at fending it off (at least for a bit) for specs/scarf Jolteons. But, you're getting rid of your ground type, so.
Even though Ground will do 4x damage on Heatran, I think you'll still find that Choice Scarf is the most common set for it, because it outruns unboosted Infernape without even trying, so.
Oh, well I was thinking of modifying the Smogon special set, but yeah. Set it up with a chain of baton pass boosts, and then send this guy out
<Technician> @Life Orb
252 Satk 128 HP 128 Spe
-Swift
-Water Pulse
-Icy Wind
-Rest/other filler
See, I plan to do Gorybyss Iron Defense x3 and Amnesia x3 then Baton Pass to Girafarig/other Agility x3 to Togetic/Togekiss/other Nasty Plot x3-6 then Baton Pass to Persian, where I continue to rip through everything like it's wet paper towel. Good or what?