Allthread is a bit too generic a term to place any values on. The standard hardware store mild steel grade is IMO not up to it, when “it” comes to structural requirements. I kinda think of it as wimpy metal, reduced in section and made wimpier still by having an endless shear plane cut into it.
I’ve not seen the scenario you describe used, and I’d think it would be far more expensive than sets of forged eyes, cables and turnbuckles.
I have been involved in the occasional use of coupled 1” grade 8 rod to suspend debris mats and staging below covered bridges…
Available from specialty suppliers – a quick search found me this one, and some values to help you in yours >
http://www.williamsform.com/Threaded_Bars/150_KSI_All-Thread_Bar/150_ksi_all-thread_bar.html