Are you into somewhat cheesy and arguably overpowered formations? In particular ones that allow you to take hundreds of points worth of upgrades for free? Well have a look at the War Convocation! You're nearly there anyway, to be honest. All you'd need to add is a unit of Sydonian Dragoons or Ironstrider Ballistarii, which might well be paid for in the points you'd save on upgrades. You're so close, I'm actually wondering if this whole post is a trap.
I don't know how it plays, but it sounds pretty nasty. It depends whether you want to be the guy who brings the formation that some people consider overpowered. I've never played Skitarii, but they would be the army I would build if I had the cash. Amazing but expensive models.
Edit - here's what a Skitarii Battle Maniple consists of:
FORMATION:
1 unit of Skitarii Vanguard
1 unit of Skitarii Rangers
1 unit of Sicarian Ruststalkers
1 unit of Sicarian Infiltrators
1 unit of Sydonian Dragoons or 1 unit of Ironstrider Ballistarii
1 unit of Onager Dunecrawlers
RESTRICTIONS:
None.
A Cult Mechanicus Battle Congregation detatchment is basically a
CAD, so your
HQ, two (bloody expensive) Kataphron troops, and you could add your robot maniple as heavy support, I think.