eager-features.el

(defvar aj--eager-features nil)
(setq aj--initial-feature-count (length features))
(setq aj--eager-features-path (no-littering-expand-var-file-name "eager-features"))

(defun aj/load-eager-features ()
  (while (and aj--eager-features
              (not (input-pending-p)))
    (unwind-protect
        (require (pop aj--eager-features) nil t)))

  (when aj--eager-features
    (aj/load-eager-features-idle)))

(defun aj/load-eager-features-idle ()
  (run-with-idle-timer 0.05 nil #'aj/load-eager-features))

(defun aj/load-eager-features-start ()
  (and (file-exists-p aj--eager-features-path)
       (load aj--eager-features-path)
       (aj/load-eager-features-idle)))

(defun aj/save-libs ()
  (with-temp-file aj--eager-features-path
    (insert "(setq aj--eager-features '")
    (insert (format "%S" (reverse (butlast features aj--initial-feature-count))))
    (insert ")\n")))

(add-hook 'after-init-hook #'aj/load-eager-features-start)
(add-hook 'kill-emacs-hook #'aj/save-libs)