I succeed to export the Validator factory via pure OSGI services mecanism (https://github.com/Tcharl/net.osgiliath.helpers.parent/tree/master/net.osgiliath.helpers.validation.osgi.services): meaning without spring-dm, blueprint... And it was not a hard task.
This module is Apache Licensed so feel free...
Note that I don't think that xml contraint mapping/definitions/resources may not work properly due to the modular OSGI classloaders (but simple default constraints are OK).
Have you got an OSGI/BVAL expert on this subject? BVAL is one of the missing things on the OSGI ecosystem.
I know a little about OSGI, but totally noob on the BVAL stuff, so I don' t think I can help more (but if you've any question, i can answer)...