They take influence from a lot of different shooters. The Overwatch team is about 75 people who are always collaborating on different ideas for heroes inspired by different games that team members are playing at the time.
Lúcio's inspiration came from the classic RPG bard, who buffs his allies with music.
Lúcio's mobility came about thanks to a need for him to be able to keep up with the speedy offensive characters like Tracer and Soldier: 76. Mercy can fly and Zenyatta doesn't need to be able to keep up with his heal targets, but Lúcio does.
Regarding Overwatch on console: Blizzard is always trying to bring their games to as wide of an audience as possible. They have a lot of experience with bringing games to different platforms, and while Overwatch is currently PC only, they are always considering how to widen their reach.
Soldier: 76 was originally a side project of Chris Metzen's, and when Overwatch was in development he approached the Overwatch team and asked if they could incorporate the S:76 character into Overwatch, with him possibly being the leader of the organization.
The hero design team was working on a hero that would be more approachable for newcomers. When Metzen approached the Overwatch team with the S:76 idea, they decided to merge the hero concept with the story concept to create the hero we know today.
Lúcio came from the design+art side rather than the story side. His concept art was used in the announcement trailer and Blizzard has had their eye on him ever since, with the intent of bringing him to the game (Interesting note here -- turns out that at least some, if not most, of the unreleased heroes that have been teased were only concept art at the time of the game's announcement, without a story/role/kit)
Lúcio's art and kit were all done before his story. Michael Chu and Chris Metzen wrote a backstory to fit the character.
They have nothing to talk about with regard to skins, they're focusing on getting the game into a playable state for beta.
There are many more heroes to come, with many amazing ideas. Kaplan agrees that there is such a thing as too many heroes, but doesn't think the game is currently anywhere close to that. They'll know there are too many heroes when a new hero just feels like a reskinned version of an older character.
One example that Kaplan gives of heroes that are similar but also different are Hanzo and Widowmaker -- both are snipers who can grant vision to their team and can scale walls to climb to advantageous positions, but Kaplan feels like they're different enough that there's no major overlap.
Overwatch is a blend of shooter and MOBA, but an in-game levelling progression system just wouldn't work with the game's pacing.
They experimented with an out-of-game talent system that allowed you to customize your hero's abilities (!!!) but because the game is so fast-paced and in first-person, visual clarity became a concern.
One example of a talent was when Reaper used Wraith Form, he could pick a talent that allowed him to heal to full. Because the game is so fast, it became too hard to tell if that was Reaper with the heal talent, or Reaper with the "move faster while in Wraith Form" talent. The game lost its predictability and counter-ability. They have removed the system from the game (phew).
Competetive/esports is something they will look at down the road, but once again getting the game playable for beta is still their main priority.
There are plans to add more dynamic elements to future maps (like the moving platforms on Volskaya).
They are open to hybridizing some map objectives -- examples in game are the joint capture point-payload maps like Numbani and King's Row. They're also constantly looking at feedback on new game mode ideas, and they've prototyped quite a few internally. The most important thing about the game is that it needs to center around the heroes -- they don't want game modes that require them to remove abilities from heroes for balance.
They don't want to focus on KDR because your team is what matters, instead of your individual performance. In the future they're going to push away from individual score and more towards how team performance.