I know it comes down to the shooter aspect for many on here, but Skyrim and Fallout does this with FPS just as well while incorporating the RPG/FPS elements. It's the preparation period within towns/cities and your personal home that allows for success while out in the field or theater of combat. Skyrim does this well while GTA V skims the bare minimum. The immersion factor has kept many coming back to Bethseda's franchises and Bungie wants to create a ten year 365 day experience so adding as much game play mechanics as possible to create player investment in their world seems to demand scrutinity. Many will joke and I put my own brand of levity in the OP on what should be added, but crafting gear and settling storage of non essential items can enhance living spaces. Destiny as a concept has a broader appeal to more than just FPS. Whether Bungie capitalizes on this remains to be seen.

Given their repeated insistence on the game being a [i]shooter[/i] first, with some RPG and MMO elements added to enhance the immersion, I suspect they'll keep any mechanics enhancements focused on improving the shooter aspects first, with the immersive elements working to enhance the core gameplay style. At least for now. They're treading on some new ground here, so they're only going to push things so far, lest they stray from the core design philosophy of the Shooter, which is what they do best. All of the interviews which discuss the evolution of the game, from concept to application, say something along the lines of "We're making the kind of game we want to make. Bungie makes shooters, but there are elements of other genres that we want to bring into this mix in order to develop and enhance the social aspect of the game". What I take away from this is that, intially, they're going to stick with what they know best and introduce the new stuff in stages, with the rest of the modifications being made behind the scenes to the infrastructure and architecture in order to allow for proposed additions later on. With this foundation in place, they can set the stage for even more radical concepts in future releases. The other thing all of those same interviews say is that they've only just begun to scratch the surface of what will be possible.

There was article on Kotaku mulling over declined sales of the last generations most notable titles. There are some factors listed in both the transition from older consoles to the next generation. But one factor also discussed was the over saturation of the market. FPS shooters are everywhere. I know Bungie is playing to their strengths, the point of the OP is developing a player investment in the game. I'm not going to invested in the weapon for long as say compared to a house or ship filled with indicators of previous adventuring in the game. I have nothing vested in Battlefield 3 as an example. Some unlocked weapons and gear but nothing really to pull me back to revisit them. Now I've played Fable 2 and 3 when they first launched and I will find myself just every once in awhile putting in the disc to see how my businesses and investments are growing the massive pool of gold within my character's treasury and just see how the Dog is doing. I'm invested in the world and events that led me to accumulate such a representation of wealth. GTA V does this with the stock market mechanic. Breezehome in Skyrim also represents a sense of wealth and accumulation due to trophys taken in forms of weapons and treasure found in certain quests. I just cannot see myself being simply invested in armor and guns only for ten years. I loved Reach and unlocking the various parts offered, but I'm not in any rush to gaze upon them like I am of my homes,economic payoff, or personal vehicles in other games. I hope they stretch themselves on the first game past what they are comfortable with.