The extlib is not designed to work from WEB-INF/lib in an NSF. Despite the fact that a few people tried it and had relative success, I can tell you that it leads to issues, as not all the extension points will be honored.
But 853 now allows you to deploy OSGi plugins within an NSF. So you can deploy the plug-ins this way and replicate them through your servers.
Also, IBM is going to support the extlib as an add-on, so this should help you getting it installed on your customer servers.