Think of any relatively unknown nation and transform them into any of the following:
1. Regional power
2. Great power
3. Superpower (bonus)
1. Regional power
2. Great power
3. Superpower (bonus)
Bengal saw the beginnings of industrialization before the British takeover, and was close to/on top of coal reserves which could be exploited. It isn't unfeasible they could become a small-hitting world power ala Italy/Belgium
Tibetan Empire, from the Altai to Indian Ocean, from Chang'an to the Aral sea.
I would also want to throw the Duchy of Courland as another power that would've got it more if they went on the colonial gig earlier than OTL.