Working a way to remove and reinstall the wires behind the beaver plate has been discussed on this forum before from memory. I think, as you suggest you need to leave a feed string (or rope), perhaps thin rope may work best if removing the original loom. Otherwise it can become a pretty real problem, very annoying and seem close to impossible. I dunno about using another wire. Soft thin rope a bit thicker than string perhaps. And perhaps two, with one tied off at each end as a spare just in case. (So you drag two lengths of string through with the loom as you remove it, and tie both in place at both ends, and use only one to reinstall, so if it stuffs up you have a second chance. I'm pretty sure there is a previous thread on this.