Singapore as a short, late game, city state challenge civ based on trade and diplomacy. Doesn't spawn unless the player chooses to play them, or is released when granting independence/through congresses. Can't control land tiles other than its city tile, but can control water tiles. Can't conquer and occupy other cities, can still destroy units and (maybe) raze cities. No access to settlers
Spawn: 1965
Leader: Lee Kuan Yew (don't think artwork exists, but some other could be repurposed, e.g. from the Malaysian civ released in 2020 if the glasses can be removed
UP: increased commerce and hammers from water tiles.
UU: no idea, they do build their own equivalent of mechanized infantry though.
UB: Changi Airport - gives extra trade routes and gold
UHV goals to be achieved by endgame - 2020 or later if it's expanded with the increased turns
UHV1: Modern military - build a jet fighter, stealth destroyer and marine (adjust numbers as necessary)
UHV2: Modern city - build an airport, stock exchange, public transport, supermarket, wharf, national park...(adjust as necessary)
UHV3: Sign and maintain 3 defensive pacts for 50 years, but don't get involved in a war during that time.
Other ideas could be having open borders to represent their good relations with everyone from the US to North Korea. Or have good relations with 90% of other civilizations. Or commerce based.