Ah, I see. This is a bit lower level than I was thinking. Still useful, but different. I was thinking about having PreAnalyzedField extend directly from TextField rather than from FieldType, and then be able to build up whatever analysis chain that you want in the usual TextField sense. Query analysis would proceed as with a normal TextField, but index analysis would smart detect whether this input was already parsed or not. If the input was not parsed, then it would go through the normal analysis. On the other hand, if the input was already parsed, then the token stream would go straight into the index (the assumption being that someone upstream understands what they're doing).
This way, in the SolrJ client you could build up some extra functionality so that the PreAnalyzedTextFields would be parsed client side and sent to Solr. In my current application, we have one Solr and N-indexers on different machines. The setup described here would take a big load off of Solr. The other benefit of this setup is that query analysis proceeds as it always does. I don't understand how someone would search over a PreAnalyzed field as it currently stands, without a bit of extra work/custom code on the client.
One pitfall to my idea is that you'd have to create a similar PreAnalyzedIntField, PreAnalyzedLocationField, PreAnalyzedDateField etc. I wish Java had mixins or multiple inheritance.