I think the biggest improvement area should be advertising.
I first discovered BB seeing an ad, at the time division 5 leagues were as competitive as division 4 leagues are now. Sure this game has its flaws, but overall it's a great game, people may quit occasionally because they don't like something about the game engine or whatever, but overall I think (especially for micronations) they quit early on because they tire of playing bots.
Overall, I think the engine is for the most part fine, we just needs to focus on advertising this great game.