custom variable classes

One thing I want to look at for 8.3 is improving custom variable 
classes. Right now these are all user settable, which makes them quite 
inappropriate for security related settings (such as which perl modules 
to load for use by trusted plperl). I'm wondering if we should perhaps 
allow something like:
 custom_variable_classes = 'foo' foo:<security_level>.bar = 'blurfl'

and providing some mechanism whereby we could ascertain that the value 
comes from a permitted source.

I know I am not the only person who has noticed that we are a bit 
lacking in this area.

As far as plperl goes, I guess I could instead use a db table to store a 
set of module names for plperl to load, but then I would have to do some 
fairly comprehensive permission tests.

Another possibility would be to provide somewhere in the catalog to 
store such info. per db might be nicer, though.

Thoughts?

cheers

andrew