Been a huge fan of dungeon siege 1 and 2, the third installation was such a disappointment for me. I have played dungeon siege for about 10 times now and it my personal best RPG. I would like to present my recommendations for the IV installation.
1) Open world : Dungeon Siege 1 has one of the best open world in RPG's history. Stick to it and bring back Chris Taylor as the designer.
2) Music : One of the best feel good music of all times, please bring it back in the fourth game.
3) Party : One of the main feature that everyone loved.
4) Skill system : Dungeon siege 1 skill system was awesome. let it be
In short Just take dungeon siege 1 and enhance it with bigger world, better visuals, loot, characters (Humans, Elves, dwarfs e.t.c), weapons, in-depth story and it will do just fine.