New strategy for assigning user to issues.
1. Given defined version can have associated "default assingee"
2. If this associated assignee is empty value – JIRA works as it happens now
3. If it has associated valid assignee – it takes precedence over component leader (and project leader too); user associated with version is assigned to issue.

This strategy is useful in situation when JIRA's "project" is treated as whole system and "version" is corelated with subproject modifying several components of system – then according to policy first responsibility should be given to subproject (version) leader.

Implementation seems to be simple to some degree and can be done as wokflow plugin. Unfortunatelly storing association data requires change in domain (and DB) model, some forms and validations – non-plugin-only enhancements are less "orthogonal" to vendor releases increasing cost of update to newer JIRA version.

cheers,
andy