You could set up domain boundaries where everything in that domain is relatively isolated from other domains. When nearing an ungenerated domain, do the proced

You could set up domain boundaries where everything in that domain is relatively isolated from other domains. When nearing an ungenerated domain, do the procedural + evolutionary generation and handle the borders blending. Domains could be tectonic plates. This would cause hitches on exploration, but they would be relatively infrequent and overall few since domains would be so large.