Topic 1: Player Housing
My thoughts on this are simple, we need a housing system much like Star Wars Galaxies used to have, a good variety of house designs and sizes, and the ability to place them freely in the world (where allowed) along with the ability to set up player towns and a town hall once the population warrants it. In addition, we'll need a crafting class that can support the housing system, ie the Artisan crafting class. *NOTE: We would want a free decoration type system, not an alloted one, what this means is that we drop and object, use a set of commands to move it, and place things where WE want it. LOTRO really borked their player housing by having cookie cutter spaces to decorate it, it isn't "personal" or fun to decorate a house that looks like everyone else's house.
Topic 2: Guild Housing
I'd love to see the ability to put in a guild keep, something we could add on, build battlements, and really get working to our advantage. I think it would be a lot of fun defending it and having a place for guildmembers to meet and what not.
Topic 3: Player Towns
Player towns would be a super fun way to pass the time, you could hold social events, set up player shops, and really build a community up.
Topic 4: Artisan Crafting Class
Unlike the current crafting professions, this would be an actual class, you would simply invest points into the proper branches (Carpenter, Metal worker, Masonry) which would allow you to create things like furniture (carpenter), Metal Barricades, Siege equipment, etc (Metal) and housing, walls, towers (masonry).
Blizzard says they are looking at ways to keep the players interested and in-game, what better way to do this than to offer the players a way to build something up, maintain it, and to really get involved if not immersed in living in the World.