In an alternative analysis of “rajul jāʾanī”, what may rajul be treated as?

Fronting the Subject: Restriction, Reinforcement and the al-Jurjani–al-Sakkaki Debate

• An accusative substitute for ism inna
• The complement of an omitted preposition
• A substitute (badal) for a pronominal agent
• The verbal noun of jāʾa