1) Location, location, location
Throughout the New Testament you see churches developing. Without exception, churches served a local area.
Ephesus. Philippi. Antioch. Thessalonica. Galati. Colossae. Jerusalem.
When churches were planted, they were planted with the entire city in mind. All were welcome. And this was controversial.
2) Strategic and temporary training and mission
Throughout the Bible, specific people and groups get special attention for the purpose of advancing God's cause in the world.
This is where Abraham, Israel, the disciples, the 120, and the synagogue strategy come in. These were all strategic and temporary.
It's so important to note the temporary aspect of niche ministry.
The end point we're looking for isn't a 20something's Small Group, InterVarsity, Men's ministry, or even a church service. In the end, we aren't gathered around a preacher. The great multitude that no one could count gathers around the throne and before the Lamb.
Niche ministry always goes wrong when we forget that these structures are temporary.