Well, Gary Seven WAS the instrument of some alien power that had been on guideing Earth for centuries.
I think it's an unwritten rule for Trek that warp drive is the only propulsion system that really works (with Transwarp being it's eventual successor; all the others really don't seem to do much), but I tossed around similar ideas where new and better propulsion systems change the balance of power.
Another idea we've all tossed around is one where Earth is attacked/invaded/conqured and eventually throws off it's oppressors. They then adapt that tech and become a space fareing race. All we know is that that first race we met almost killed us all: When that Vulcan Scout ship shows up, will we let them land, tell them to buzz off or shoot them down.
Do we become an aggressor species?
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"Yes, it's the Apocalypse alright. I always thought I'd have a hand in it"
Professor Farnsworth