Which interpretation best fits “لَيْتَ / هَلَّا” in context?

Inshāʾ and Tamannī: Requests, Wishing, Exhortation, and Reproach

• The five requesting forms — Wishing, questioning, command, prohibition and calling.
• Wishing versus exhortation — Would that / Why not (do it)?
• Wishing for the unlikely possible — Would that I had wealth so I could give charity.
• Why use hal instead of layta? — Is there an intercessor for me? / If only there were!