First thing SAARC is all about South-Asians countries with common culture as India's. How much, the Pakistanis or Bangladeshis cry that they are not part of the same cultural group, but they are. India/Pakistan/Bangladesh share the common values, language(Urdu/Bengali), food, literature, music and historically they been part of the 'Indian Subcontinent'. The idea of SAARC was the extension of same commonality to business and other resource sharing.
And, now anybody proposing China as South-Asian should be out of his/her mind, as neither China shares any cultural values or food, music, literature, language and never been part of the 'Indian Subcontinent'. Neither China can provide any benefits to any of the members by being in SAARC.