since the standard reader macro for arrays only creates simple arrays,
  you would need to call ADJUST-ARRAY afterwards to set further options, or
  create a specialized reader macro or even use #. and write out a call to
  MAKE-ARRAY with the :INITIAL-CONTENTS keyword to include the contents.

  ADJUST-ARRAY is specified to signal an error if one attempts to add a
  fill-pointer to an array that doesn't have one.  sorry.

| 2nd: how would one create a reader macro?

  see SET-MACRO-CHARACTER and SET-DISPATCH-MACRO-CHARACTER.

  no.

| (defun |#(-reader| (stream subchar arg)
|   (declare (ignore subchar arg))
|   (make-array :adjustable T
|               :fill-pointer T
|               :initial-contents (read stream t nil t)))

  try READ-DELIMITED-LIST, instead of READ.

| second, the arguments to make-array are wrong.

  yes, you would need to read the list first, then use its length as the
  dimension.

| i believe this are ignorant questions, but having never ever thought
| about modifying the reader, i have to ask for more help.

  I think you should hold back on modifying the reader.  it's not a good
  _first_ thing to try.