Ensure path exists before using it

I want to improve this bit of elisp code ensuring that bash-path 
exists.

    (let* ( ;; Relative subdirectory that doesn't start with / or ~
            (subdir (or subdir "orellana"))

            ;; Determine the base path: argument, directory, or env var
            (base-path
                (or bspt
                    (and (file-directory-p
                           (substitute-in-file-name
                             "$HOME/Opstk/src/hist-1.0/"))
                         (substitute-in-file-name
                           "$HOME/Opstk/src/hist-1.0/"))
                    (expand-file-name "~/Opstk/src/hist-1.0/")
                    (getenv "ORELLANA_PATH")))

	    ;; Construct the full path to feature
            (ftpath (expand-file-name subdir base-path)) )