There is no magic. they have to put things in their classpath.
Just checking ... sometimes you and Uwe bust out stuff that is indistinguishable from magic.
But I think we should fix the examples and support (as the "new" syntax)
Hmmm... yeah i'm -0 on that part ... i mainly just worry that it would be confusing for users if some places in the config (charfilter, tokneizer, tokenfilter, analyzer) supported these short names, but other places (fieldtype, requesthandler, serachcomponent, etc...) didn't and required a FQN ClassName or solr.ClassName
FWIW: The other issue to consider here is how the packaging of these "uber-module-jars" will work in Solr binary pacakges ... right now it's the solr contribs that provide the factories that ensure the lucene modules they depend on make it into the final tgx/zip files ... if lucene modules start providing the factories themselves, we'll need some build.xml shenanigans to copy those module jars into the solr package dirs.