[Mooff]

plugin with hook location bbcode_(something) (check the php file for which hook you need) and some if condition whether you are in the bbcode_quote. There the quoted text should be in the variable $code, use some php functions like strlen($code) to find out how long it is and if it is above 1000 characters or something manipulate it to $code = substr($code, 1000) and $code .= '<a href="">read full quote here</a>'.