かっこいいかは知らんけど、split-sequenceを使うと、

(defun omanko (src)
(mapcar (lambda (s)
(mapcar (lambda (x) (coerce x 'list))
(split-sequence #\Space s)))
(split-sequence #\Newline src)))

(omanko "わたしは 太郎 です。
趣味は ２ちゃんねる です。
Lisp初心者 です。")

↓CLISPでの結果

(((#\HIRAGANA_LETTER_WA #\HIRAGANA_LETTER_TA #\HIRAGANA_LETTER_SI #\HIRAGANA_LETTER_HA) (#\U592A #\U90CE)
(#\HIRAGANA_LETTER_DE #\HIRAGANA_LETTER_SU #\IDEOGRAPHIC_FULL_STOP))
((#\U8DA3 #\U5473 #\HIRAGANA_LETTER_HA)
(#\FULLWIDTH_DIGIT_TWO #\HIRAGANA_LETTER_TI #\HIRAGANA_LETTER_SMALL_YA #\HIRAGANA_LETTER_N #\HIRAGANA_LETTER_NE
#\HIRAGANA_LETTER_RU)
(#\HIRAGANA_LETTER_DE #\HIRAGANA_LETTER_SU #\IDEOGRAPHIC_FULL_STOP))
((#\L #\i #\s #\p #\U521D #\U5FC3 #\U8005) (#\HIRAGANA_LETTER_DE #\HIRAGANA_LETTER_SU #\IDEOGRAPHIC_FULL_STOP)))