I don't know what you mean for sql/xml-rpc. There are functions to query a database or to issue xml-rpc requests, however I don't see what a plugin doing both is :)

>
> Another aspect : the priority is clearly Mageia-bugzilla, but would it be
> reasonable later on to try to take on (some) upstream bugzilla's ?
>

Reasonable I don't know, but why not. doc4.mandriva.com seems to link to debian's bugzilla. However, linking to upstream bugzilla's may be outside mageia-app-db's scope, however nothing prevents from studying its feasability.