> However, I'm not sure a singleton classloader reference works well from a redeployment perspective...

Really, that's the biggest issue.  It defeats redeployment, dynamic bundle contexts (especially a bundle getting added/removed in the middle of runtime), etc.  However, most of ISPN is not setup for that anyway.  At least within ORM, having a core or client bundle get restarted during runtime would be catastrophic.  We have a lot of work to do to support being fully dynamic.  And I'm guessing the same is true for ISPN.  If that's the case, singleton might be an acceptable baby step.