Homogeneous churches?

I thought I would venture a post on this most controversial of topics. It is, obviously, highly relevant given the fact that so many people are thinking about church planting these days. As an initial point, I guess we have to be clear about the difference between "natural" and "prescriptive" homogeneity in a congregation. "Natural" homogeneity (NH) means, here, the fact that any community tends to attract certain kinds of people and develops a certain kind of ethos depending upon the leader, music, preaching, location etc. This arises naturally and probably gradually but is not an overt philosophy of ministry. It is not intentional. "Prescriptive" homogeneity (PH) means, though, a designed and intended strategy leading to a mono-cultural congregation. The justification for this is the need to better evangelize and disciple certain groups of people. It follows on from an approach that assumes 'target groups' - in a way not dissimilar to marketing strategies.

Now, I fully agree that the gospel needs contextualization and culture needs to be taken very seriously in mission, but these are my problems with PH:
1. It's in great danger of generating spiritual apartheid. It will simply reproduce existing social distinctions in churches. Isn't it actually a point that the gospel generates counter-cultural communitites that overcome these distinctions? PH has a strong tendency, therefore, to cultural conservatism and thus worldliness.
2. PH sees the witness of cultural relevance to be more important than the witness of a diverse community united by the gospel. It has a very weak ecclesiology and fails to see that a unified, loving community is our greatest evangelistic tool.
3. PH is in danger of distorting the gospel in that the meaning and implications of the gospel can only be fleshed out in community. If that community is monocultural there is a greater danger that it confuses its own values/approach with that of the gospel. Christians from backgrounds different from me teach me something more about Christ.
4. PH, though it seems evangelistically-motivated, will ironically quash a missionary spirit. Certain groups will be reached but others won't. Churches trapped in one culture will often only 'see' their own group. Further, they will be poor at training up people to relate to the Other!