Do we need the old printers?
As this is an independent rendering engine, I guess it's better to give the opportunity to people to choose between the default and the secure mode. We can imagine having some usecases where we don't want to clear javascript for example. That's why I think we would need both the printers.
I guess that as an independent rendering engine, it would be good to have the ability to have a full wiki->XDOM->XHTML pipeline.
As a secure independent rendering engine, it would also be good to have a secure XHTML output, without making the (API) users do extra work to get the security working.
Yes that's why I've also introduced secure blockRenderers and renderers.
So it's easy to put them in the API methods (that's what I've done in XWikiDocument.renderXDOM()), and the API users won't have to do some extra work.