Find duplicate paragraphs - or similar paragraphs

A rare feature we desperately need, An intelligent system that can find identical paragraphs, and maybe almost identical paragraphs based on % of words that are identical. This could then be displayed in 2 side by side panes, with a line number against each line. It would list first instance on left pane, and next instance on right pane. A list of consecutive paragraph matches would proceed down the page and allow for syncronized scrolling of both panes. ie paragraphs in panes lined up exactly for easy visual inspection.
eg
p1 p1a

p2 p2a

p3 p3a etc

Option to define paragraph as a sentence ending in a full stop, or a group of sentences ending in a carriage return.

Option to process x lines of text in a document starting from line xxx. Or to select block of text to be processed within a document. ie to speed up processing of text within very long documents.

Please advise me of your progress.
thanks, Ray