Scrangos - any raider going out front will still let you know that your opponent plopped a gunship plant, even if it fails to get any other useful info or do any real damage. That's enough info to get you putting out enough AA to mitigate a gunship rush. With
any lab one of your first actions needs to be using a raider or scout to do as much damage as you can and get as much info as you can, and that will help handle any RPSy rushes.
Techswitches are less scoutable, but a techswitch and the following lull while your opponent builds up his new switched offensive force is going to
seriously hold back his ability to handle you at the front. That should tip you off that
something is up and also give you the opportunity to make some serious headway, maybe enough to render his techswitched-onslaught a moot point.