Good question
Don't know about pb, unfortunately it
seems pure doesn't like it (images won't load).I know there's a cml.pk3
for his HUD which seems to auto download itself after I deleted it.
Don't remember if that came with the e+ update whether it's just on the
servers I connect to.
I can post it when it's done, and if you want
to use it with pure enabled, it's up to the server admin to allow and
uplod it.What's the community's opinion on this? Should there be a
process (someone high enough to validate its safe or something)

I don't know about punkbuster, but I'm pretty sure pure will kick you with extra *pk3 file, if there is just that change for graphic of HUD I don't see any hazard to implement it on servers, but it's still owners decision to allow it. Anyway none of HUD cfg edits will make you suspected as long as it is using known *pk3 files to make it working.