I figured you probably did. Long post… sorry.
My recommendation is try BCL. The requirement is that you tech straight into it (build order honestly isn’t much different than any of his general build orders).
Super Gary covers air generally quite well, there will be very rare instances that air units is so heavy (and armored) that gives him trouble. Meanwhile, BCL require Mecha Corruptors anyway so you can always make good use of them. One thing with BCL build I will note is that it isn’t like mass Mecha Hydra that you can obviously make a ton then push out. The ramp is slower but even 2-3 BCL can make an effective push. And as always, Overcharge with pushes, as BCL are super expensive comparatively, losing a few early on will hurt your speed.
Other viable builds, some of which are mentioned include: mass Mecha Hydra, mass Mecha Zerglings (works best on PP and DoN), mass Mecha Infestors (which is honestly super boring).
A few traps for him would be: Mecha Banelings (whilst supposedly the damage cap is fixed, it is still quite a cost-inefficient build, nowhere the same Zagara feel but a fun little build to play around nonetheless). Mecha Lurkers remain absolutely terrible. Mecha Ultralisks is again more for decorative mix and matching with other builds. Going pure ultras works but is basically a cooler version but less effective ling build.
All of that is just my experience playing and observing other players. Nothing really new. The macro portion is the same, you’ll always want Super Gary out first regardless. Some have opted to do a proxy hatch, which works well too. Overall, with/out the proxy hatch, it doesn’t affect the general streamlining of Stetmann.
A few notes about prestiges:
P1 loses you Super Gary, so your engagement will not be nearly as well protected, so I recommend sprinkle some lings in to help out.
P2 is practically is just a straight up buff. Nobody should be engaging without Stetelite whenever possible. So if that’s becoming an issue for some reason, the key is to spread those (like creep) more properly.
P3 I am unsure of in terms of any specific changes. It simply costs more and the benefit isn’t extreme from what I understand. That said, I haven’t tested this one at all or seen many use it.