The solution to Borderlands being "populated" with an excess of guns.
I was thinking about how many gun there was being dropped by creatures, robots, mercs, pirates and even popping out of boxes they could not possibly pop out of.
Then I had an idea.
What if instead of complete guns, parts or portions of firearms popped out. You could have a 100% of creating a moderately powerful firearm.
Or ... you could have a slim chance of putting together some potentially powerful weapon is powerful.
What if a firearm just didn't have to use up shotgun shells OR rockets but instead could have an element of BOTH? The shell would explode on target and release a shotgun like explosion, using a portion of both shotgun and rocket ammunition. In Borderlands, it seems we never run out of ammo (at least 80% of the time).
Make it so we could be wielding a weapon that WE put together that is unique to us and you will have a best selling game.
Maybe a grenade launcher that shoots the grenades from your grenade slot and when you run out of grenades, it shoots 10 shots worth of your shotgun ammo, I don't know! Maybe have a specific class that constructs weapons and has little combat value? Make it a truly co-op game.
Secondly, open up the world and make it seamless.
Third, give us verticality - jetpacks.
Fourth, I know you have friendly fire from our own hand-wielded weapons, but what about the turrets? It seems a little far fetched to have our turret blasting rockets and NONE of them hurt the wielder of that turret. Also make it so you can vote for friendly fire as long as everyone agrees, maybe?
Fifth, maybe normalize damage, hit points of creatures and difficulty for other players who have a higher level character than you. Make it an option that my level 21 Commando can go through missions with my friend who has been playing for a longer time with her level 43 Siren. This way the level 43 Siren does not wipe the floor with everything while I hide behind a rock having all the fun of watching her play.
Concerning the Turrets for the Commando, make them much less accurate and powerful unless the Commando controls the turret. This way, the commando could be exposed in exchange for the turret being as accurate as he is. Maybe instead of a stock machine gun and rocket launcher, make it so the Commando can put any two weapons he picks up on the turret chassis! The weapon would fire slower and may be less powerful, but it would add interesting tactics to the game. A double shotgun turret that is deadly and a double rocket launching turret that shoots 6 rockets at a time (that are less powerful).
Lastly, in my opinion, every encounter in an RPG should be moderately difficult in that there is a more than a 75% that you could lose something you don't want to lose. It doesn't necessarily have to be the loss of the character's life where you are "respawned" at the beginning. It could be the loss of equipment you worked so hard for, loss of "experience" or loss of abilities you had temporarily. If the game is difficult to play, it will be more enjoyable when you eventually overcome that difficulty.