Most recent version of a Nexus Kate MWL list, inspired by the original Nexus Kate 2.0 (http://netrunnerdb.com/en/decklist/29419/nexus-kate-v2-0) list.
The biggest issue I had originally was feeling like there was never quite enough time in a turn. Magnum Opus is an inherently limited engine and there's no way to burst up like you could with Prepaid. Technical Writer is an attempt to mitigate that as getting one early means you should be able to pop it for at least 7 or 8 credits when you need it. I'd prefer Stimhack, but I'd also prefer Clone Chip and Lady.
One Symmetrical Visage is included over one Earthrise for the same reason - it just helps you keep your momentum up a bit. Briefly considered Professional Contacts, but that and Opus is far too heavy.
Currently it's 46 cards because I just really like the flexibility of this breaker suite. However, it's very possible - probable, even - that I only need 1 Atman and can rely on Nexus to deal with high strength sentries reliably.
Regarding Lady vs Snowball - I still wouldn't build a Shaper deck without two Lady, 3 Clone Chip. Two influence is a small price to pay for the best barrier breaker in the game, and the incredible flexibility of Clone Chip is something I can't pass up. Clot is included because NEH Fastro is still very much a thing and this deck needs a way to slow it down.
This deck has been very effective in testing so far. The Nexus combo is incredibly oppressive once you get it online and I feel this is stronger than a vanilla Shaper with ProCo. That said, it's not as strong as Prepaid was and I also don't think it's as strong as Noise is.
I've been seeing Security Nexus shapers seeing a bit of play lately, and I think they are very strong. Security Nexus is indeed very powerful with Rabbit Hole.
With Magnum Opus econ, and so many programs, I'm not sure Mimic + Datasucker are really stronger than GS Shrike M2. Shrike costs more to break with, but can be boosted to deal with large sentries without Datasucker support. This frees up 2 MU to allow more flexibility to use SMC, or use Atman freely.
I've seen these builds use Professional Contacts most often, but I think ProCo + MOpus may eat up too many clicks, so the clickless draw from Earthrise Hotel may be an improvement.