Follow-up of this comment: https://issues.apache.org/jira/browse/LUCENE-6818?focusedCommentId=14934801&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14934801
Index-time boosts are a very expert feature whose behaviour is tight to the Similarity impl. Additionally users have often be confused by the poor precision due to the fact that we encode values on a single byte. But now we have doc values that allow you to encode any values the way you want with as much precision as you need so maybe we should deprecate index-time boosts and recommend to encode index-time scoring factors into doc values fields instead.
SOLR-2029 Support for Index Time Document Boost in SolrContentHandler