I think I originally thought up this concept using old airplanes. But old ships, or anything large that floats, and no longer usable or needed in the intended service. 

Then building functional cities by bridging multiple together.

The thought is basically this is temporary, even if longer term. The cities would be anchored near the place fleeing from, at a safe distance, or an acceptable location hopefully with a similar culture.

I'm thinking sterilization would be a requirement of staying on board. It's going to be bad enough with pregnant arrivals, babies and small children. There is no need to increase the needs and reducing space. Although not intended as permanent, it should not be easily reversible at the expense of being effective.