So problem after update with new ores (for example that new blue ore for paint) is, that you won't find it unless you start with a new map or travel far away. And many servers even have expanding disabled, so there is no way to get new ores. What about having a plugin that will generate new ores? So admin would run this after update and plugin will replace random stone blocks in underground with new ores. Plugin would make note of already generated chunks, so no chunk will get ores multiple times. If player loads chunk, where new ores were not generated yet, plugin will generate them and then add to the already generated list. Once all existing chunks are generated, plugin will disable itself.