I hope that "would let him leave for free" would carry the understanding that we'll be the one Vela goes out on loan to. Multiple birds, one stone.
I don't think he'd get enough games with you for Wenger to send him on loan, i don't think he'd want Campbell THAT much to sacrifice Vela.
If pardew wouldn't start Carroll + Vela every game possible there'd be major questions asked of his mental faculties.