A great way to do this!  One thing I noticed is that the consecutive REPLACE functions at the end of the SP don't really do anything (i.e. they replace '<' with itself).  I changed the code to this and it seemed to work: 
... + REPLACE(
            REPLACE(@BodyHTML, '&lt;', '<') ,
            '&gt;' ,
            '>') ...

Note: I have not fully tested this so use at your own risk 🙂

Thanks for the innovative approach 🙂