I found my draft rep, and now put it on github:
https://github.com/tkruse/rep/blob/nodeparam/nodeparam-REP.rst

Note this was work in progress when I stopped working on it.

Other things I considered back then:
- whether to support complex parameter types like poses (rather than 
just primitive values)
- how to organize parameter naming (I think there were some 
inconsistencies between rospy and roscpp around the '~')
- using the same system for logger levels
- grouping of parameters instead of having flat lists
- whether to support batch updates of multiple parameters as one 
operation (e.g. when parameter validation would else deadlock changing 
two interdependent parameters)

cheers,
   Thibault