I'm making a civwars-esque map... got everything cleverly worked out but still hanging on this one problem.
You create units at your base, each unit you creates adds to your spawn. every 20 sec a comp player spawns the units youve created.
I want to add the ability to upgrade to add some depth and give the ability to make stronger units cheaper than getting the prereqs for a new unit.
But, of course, when a human player researches upgrades, the computer player's spawns will still be unaffected.

I've tried giving the player's buildings to the computer in charge of spawns, right before the spawn happens, and give them back afterwards. it didn't work.
i tested it, and even after my engineering bay had been removed or given away, Create Unit triggers still gave me upgraded rines.
Give Unit triggers that gave a non-upgraded rine to me, turned it into an upgraded rine. But giving the comp my Bay didn't give him the upgrades.

I know you can start the comp off pre-upgraded with map settings, that's not what i want. I want to have him spawn 0 / 0 marines for a bit, then i research armor, and he starts spawning 1 / 0 marines. etc.

Is there a way to do this? Maybe an AI script that simply says "research this with your engineering bay?"

You can give tech (like stim) to the comp by giving him a unit by triggers that has this tech researched. But that doesn't work for upgrades.

You could give the comp some melee ai and money and hope he will research it on its own some time. Thats all.

There's no ai script that can tell it so specifically as you would like

In some games I have played however that you have a computer ally, such as in Gunship Assault RPG, the computer sometimes upgrades itself, but other times it doesnt, so I guess its just luck of the draw.

Where can I get this Gunship Assault RPG ?

From Starcraft.

Some AI scripts tend to upgrade certain things more the others, I've found. The best person to contact would probably be Gidoza, I remember he told me about in his map how he managed to force the computer to research certain upgrades before others, so that ground would be upgraded before air.

You'd still have to deal with the problem of them sometimes researching it, and sometimes not, though.

Giving away a researching building simply cancels the upgrade.

Try experimenting with the different AI Scripts that SCMDraft2 or SCXE offer, theres all sorts of them.

They always start with more than enough money. Start a new map with a computer player and save a replay to verify this.