I actually quite like the idea of a Biafra civ (I've been bouncing the idea around for a short while, actually). And I do agree that it could be nothing but late-game uniques, but that doesn't seem to be a problem for any of JFD's WW2 mods, for example. Churchill has a Battleship Replacement, a Fighter replacement, and a simple production-boosting UA, yet I would still call them fairly strong to play as all game long. That Biafra design is pretty solid, but I do agree that a few slight changes would help.
For starters, I do think the Biafra Baby would work best as a Bomber replacement, instead of a Helicopter Gunship. Perhaps available earlier, with Ballistics. Some sort of bonus to aircraft is also necessary, whether through the UA alongside Armor, or through some sort of "Recruit Jan Zumbach" decision. (Perhaps the latter could simply grant a bonus to the production of Aircraft, and provide a unique Ace unit that functions like an Aerial Great General.) Additionally, the straightforward combat bonus to Armor (and Aircraft) gives off a bit more of a "Blitzkrieg" vibe than an "Araba Let's Separate" vibe. Perhaps, at the cost of making it needlessly complicated, they only receive the attacking bonus when fighting within 2 tiles of the empire's borders, inside or outside. So as a final compilation of my ideas:
Republic of Biafra (Ojukwu)
Start Bias: Coastal
Capital: Enugu
UA:
Araba War
Upon a Declaration of War, generate +1
Production from all Strategic Resources and receive double Oil for the duration of the conflict. Armoured Units and Aircraft gain a +25% Combat Bonus when attacking within 2 tiles of the empire's borders.
UU:
Red Devil (replaces Bazooka)
Radically different to, and slightly weaker than (78
Ranged Combat Strength vs. 85), the Bazooka it replaces, the Red Devil is considerably faster (base movement is 4), may move after attacking, starts with +1 range, is available at Combined Arms rather than Nuclear Fission, counts as an Armoured unit, and requires Oil. Additionally, it has a unique promotion, "Ogbunigwe", that allows it to deal damage (with a -67%
Combat Penalty) to all other units within 1 hex of the target, including Cities and friendly units.
UU:
Biafra Baby (replaces Bomber)
Available with the discovery of Ballistics, the Biafra Baby is cheaper to produce (325
vs 375) but slightly weaker (62
vs 65) than the Bomber it replaces, though it also receives a notable combat bonus (25%) when attacking targets in Open terrain.
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I tried to differentiate the Biafra Baby from the B17 (the only other Bomber UU I know of) as much as possible, which means sacrificing the bonus against cities. But the cheaper cost + the UA's bonus to Aircraft + the potential Decision boosting both of those things significantly means I had to make it a bit weaker by default, as well. Either way, any units dumb enough to set up camp in open terrain within 2 tiles of your border are dead meat.