I think this would be a fun way to reinvigorate the game for long-time players. It may be too development heavy to be done though - new classes and gear for those classes (like in SS) would be a lot of work. It would be great to have a way to play back through the game in different classes, with new class specific gear, class specific quests, enemies and story lines inserted into existing content, to make it new each time through, but that is a ton of new content to be created, and ultimately will it pay back the investment in time and resources for HCS? They'd need to do a feasibility study.
Given we aren't getting some upgrades to chests and arena that have been asked about forever, I think a radical overhaul (essentially creating a new game as a continuation of the old) like this is unlikely to fly.
We can dream though! I like it.