I hope any such effort won't be stopped by not quite positive post I made.
The OP query is too vague IMO, modernizing could mean making it 3d, it could mean graphic 'improvements' which would give photo quality to chars, maps, both stupid IMO - which is not to say that graphics couldn't be improved. Game view could be larger, even full screen on today's monitors, to allow view of wider area - computers and internet are beefy enough nowadays to handle that (to keep track of more mobs in player view without lagging) but I suppose the game as such as it is wouldn't utilize that bigger view.
I would like to see besides caves maps where you would wade waist deep in water, fight water mobs like sharks, piranhas, water dragons surfacing from water, even swimming should be possible (various new items for that including air breathing masks...), there should be islands/lands reachable only by swimming (maybe timber could be used to build rafts of various kinds to sail to far out lands, fighting mobs spawned out of water attacking the raft/chars on it, there could be diving into a maze of water flooded tunnels which would lead to caverns with mobs, you could be attacked in the tunnels by water monsters, if your air would be used up you would die... there would be items holding air or maybe third indicator besides HP/MP showing how much air you got in lungs... and you would be able to dive for longer if your air supply would be larger by training diving skills, there would be swimming skills.
Whenever I see zombies in mines, I think we should have 'egyptian' theme on some maps, with pyramids, looting sarcophagus with Pharaohs as bosses, Egyptian gods as mobs and bosses (like those pple with birdheads, ptah's), riding on chariots towed by one or two horses, fighting with spears while riding them (mobs would run away until you caught up with them and hit them once, then they would turn on you, some would keep on running away and you would need better horses to be able to hunt them down, kill them), conducting wars while riding on chariots...