How to mess with campaign upgrades?

I was a decent user of SC1 Editor back then, but SC2 Editor took more time then I thought just to figure where everything is.

Say, I want to edit a campaign map so that I can use upgraded/variation units that shouldn’t be possible at that point. For example, play the first terran mission with Shield+Stim Marines, the first mission on Zerus with Broodlord, the Karax mission with Tal’darim Mothership, etc. As far as I’ve found out, each campaign mission checks for the player’s tech options in the initialization stage. I wonder if I can override that, and tell the map to give me exactly what I specify.
There aren’t such a global variable thing thoughout a campaign back in SC1, so I don’t even know where to begin to look at. I appreciate any hints that can helps me get started, many thanks.

The action “set upgrade level for player” should work for most things. Probably have it activate after all the initialization stuff. The event “time elapsed” set to 2 seconds should work fine for that.