I mean, you could write your own spec-outputting function that works like you describe 🙂

This is not what you want, the failure message would not be very helpful. But just a back-of-the-napkin sketch to inspire you 🙂

(defn map-spec [validation-map]
  (s/def (fn [input]
           (and (clojure.set/subset? (set (keys input))
                                     (set (keys validation-map)))
                (->> input
                     (filter (fn [[k v]]
                               (contains? (set (keys validation-map))
                                          k)))
                     (map (fn [[k v]]
                            (let [validation-fn (get validation-map k)]
                              (validation-fn v))))
                     (every? identity))))))