You make a good point, but elaboration is required... ideas aren't going to kill G0-T0
I'm not as samrt as Plagueis, but I'll try: He could hide on a world with a culture far different from the galactic standard and control his operations from there. Let's say, for example, Voss. If he is enough of a threat, G0-T0 would turn his attention there. But most of his power base are droids and won't be able to adapt to the culture. And they also can't simply ignore them or blast their way through them. And everyone else G0-T0 sends won't be a match for Plagueis.
If that isn't allowed, Plagueis could develop a new culture, a completely new code of honor and combat rituals for his Sun Guard. Something G0-T0 is not familiar with. For example, let the command shift after 15 minutes of battle. Order them to take droids prisoners. Let them attack primarily low priority targets. All in all this might wear down his powerbase. (I would need much more time to develop completely new but still decently effective strategies, I hope you see the genereal idea, though.)
Unless Darth Plagueis is an expert computer programmer, which he probably isn't, that isn't likely to happen. Also G0-T0 probably passed the threshold into having consciousness, the droid had imagination and a deviousness that is hardly ever seen in a droid.
Even if G0-T0 passed that point, he would still be at the start of it. The general idea is to confront him with situations he isn't prepared for. Even at this point of consciousness, G0-T0 would probably have problems to adapt to things which aren't in his original programming.