One grammatical proposal for «رجل جاءني» is not to reconstruct the noun «رجل» as the verb's direct agent in a later position, but as a substitute (badal) for a pronoun. On that account, the verbal agent and the noun substituting for it are kept distinct.
The objection is that, if the aim is to preserve the rhetoric of fronting, why must the reconstruction through badal be the only possible explanation? Different syntactic readings may not carry identical implications.
The lesson is that the rhetorical force should not be fixed before its possible parsing has been examined.