WvW needs something now, not next year. So, why not add one copy of the EotM to the existing WvW maps? Make it count for PPT just like borderlands and eternal, maybe slightly less than the original maps but something significant and call it Battle of the Mists
The could leave EtoM as it is, a megaserver WvW map for ktrains and overflow. It seems like that could be a pretty low effort addition to WvW with low consequences, if things got really unbalanced just go back to the 4 maps. Make it a live beta test, I don’t think anyone in WvW would be upset to beta that map in regular WvW. The could start with the PPT contribution low and gradually increase it as needed. Spoon