shugs,
I got pretty much that exact scenario in my s3 (it was hypothetically southampton so only one runway). The ATCO kept asking me if I was going to reopen the runway, even once everyone was out, debris cleared and fuel offloaded etc, and even if the last 100m of the runway were off limits and aircraft were taking off away from the crash. I kept saying no (he was ridiculously pressuring.. I almost caved)... but kept saying safety first and all that, and used an example I'd seen on a tower visit to Machester to say that there's always room for pilot error (if he ignored the 100m, turned round and clipped a wing and caused even more disaster they'd never believe you opened the runway...). You're then having aircraft take off downwind which causes even more risks...
I got through, so I'd say stick to the safety aspect, but give a reason how you think the situation could compromise safety.
Good luck, you're sounding pretty damn prepared
Abi