Well, the lisplike we use in the office doesn't have modules either, so our convention (actually just my, since no one else takes that language seriously) is to put a prefix name like yours.
Btw there might be a bug in 'arglist-vars - it uses (is arglist 'cons), maybe you meant (isa ...) ?
LOL. In my off-time in the office I'm building a package system for that lisplike, basing off a macro that must enclose all forms that need to use packages; basically what it does is add the package name to the symbols that have been imported from the package.
Also, for 'arglist-frees - from what I can hack, it tries to extract used variables in argument lists for optional arguments. So for example, your intent is that:
(arglist-frees '(x (o y (some-var))))
=> (some-var)
However, to extract the subexpression, you use car:cdar. I don't understand why.