I feel like it's OK not having rest args if you leave them out in order to support currying, but leaving both out seems really weird for a language that's trying to be functional.
(defmacro foo args
(do 'something (with args)))
(and (>= (length args) 0)
(=< (length args) 255))
Edit: Oops, Robert mentioned this, too.
Even syntaxes which have OAIPA can (and do) still have optional parentheses to exactly delimit the arguments of a call, and that notation can clearly support variadic args.
Outside of explicit delimiting with parens, OAIPA can work on a variadic function up to its required arguments by considering it to be a function of exactly that number of arguments, and no more.