-Map design: A map should be made so that there are a LOT of places to go to without promoting camping...
SMART will allow players, especially light characters, the ability to move around the maps quite dynamically, with only heavy players limited to mostly traditional paths. In addition, SD has done everything they can to prevent camping, as they are not a fan.
-Explosive weapons: care is required when balancing those, they need to be powerful enough to be useful but not too strong it quickly becomes a game breaker (mw2 is a perfect example of a fail explosive balancing). For me, the best explosive balancing is in BFBC2 (apart from the c4 on explosives)
There are no one-hit kill weapons in Brink including grenades and grenade launchers - the only explosives. Grenades will mostly be for crowd control, knocking over opponents, and indirect attacks. There are going to be a few abilities to improve grenades in various ways, with most of those skills being for soldiers.
-playlists: make playlists for beginners and advanced players...
There has been mention of matchmaking being able to group players of similar skill together, but for the life of me, I can't remember how they said they intended to do it.
-SKILL!!! If you want people to play your game for longer... put things in it that require skill, let the best guy/team win! I'm thinking of a feature like promod in cod4, that was a pure skill based mode... same for Quakelive: if you were the best, you won, even in team based mode... you do not have to make the entire game a skill based game but at least a playlist or something for more serious gamers...
All FPS games are primarily skill based, as everything depends on your tactics, aim, and reaction, as well as reading the opponents. That being said, SD has tried to put more focus on teamwork and team skill than individual skill. Having a game mode where one skilled player on a bad team can still win the game goes against what they have planned for Brink. They have said multiple times that playing as a lone wolf won't work very well at all.
-Spawn points: we have all seen how a bad spawn system ruins a game (mw2, moh, black light tango down) and rewards spawn trapping too much as well as making it too easy.
Brink has command posts and multiple spawn points that allow players to continually spawn close to the action as the game progresses. In addition, SD has done everything they can to prevent spawn camping, to the point of putting indestructible turrets near the spawns, with a warning if you get too close to one.
-Reward team work (BF, MOH)
This is pretty much the whole game. The game is designed from the ground up to reward teamwork. All actions that help teammates give large XP bonuses, buffing teammates has a smaller energy cost and cooldown than buffing yourself. The mission system even gives options to help teammates and rewards you more XP for completing them.
-Include a 1v1 game type or event to challenge friends and mess around or practice shots in smaller maps (may not count towards overall experience... just like in reach or cod)
SD has said that room sizes are adjustable, with 8v8 as a max. Even if that weren't the case, you could always make a private room without AI.
-A split screen (the cod have a fun splitscreen mode)
I'm lead to understand that there will be no splitscreen mode in the game.
Sorry if some of my answers seem blunt, there was just a lot to respond to.