I agree with Plakat. I find it very unlikely that Beyerdynamic would condone a modification of their headphone, much less honor a warranty after one is done. You can reach out to an authorized repair agent (I used Peter at The Sound Surgeon for my last repair, peter <at> thesoundsurgeon <dawt> com, Moon Audio is another, I believe), but I highly doubt any T5p would be warrantied after modification.
Then again, I don't know how much time you have left on your warranty, but it might be worth switching just to get away from the semi-notoriously problematic cable Beyer used stock. Either way, please let us know what you decide and how you make out!! Best of luck!!