Examples of errors:
Although such might be analyzed as a pronoun--i.e. substitute for a noun phrase--in sentences like
He's a good man and is known as such to everyone (i.e. as a good man).
the fixed expression as such could just as easily be seen as an adverbial, equivalent to 'in this way'. In any case such never has enough independent status as a pronoun to be modified by a relative clause or prepositional phrase. Relative constructions should not be confused with comparative clauses introduced by such, as in
His bravery was such (i.e. so great) that he had no equal