One of the things I loved about the game was the Infected. They were believable, interesting, grounded and fierce. The Last of Us did something that almost no other video game has done before. They made each enemy feel unique, that each enemy was a human being unlucky enough to slowly lose their humanity and become one of the infected.
I am not saying that Bloaters are not possible, but they were the only infected that felt "Gamey". I did like the fact that the Bloaters we not just generic bullet sponges, I just felt that there could have been another type of infected that was a better fit in the universe. If I were to be asked to design a new infected type for a sequel for The Last of Us (or DLC) I would pitch a new less aggressive infected, The Wanderer.
The Wanderer is the next step after the Clickers in the infected life cycle. The Wanderer is sprouting spores all over it's back and head. A Wanderer is created when a the host body of a Clicker can no longer sustain the Cordyceps host.
The virus knows that their host body is near death. The Wanderer searches for a dark, claustrophobic area so that they may drop down, die and release their spores to continue the life cycle.
As they walk around they leave behind a trail of deadly spores(just like a moth) and on occasion they have a seizure which causes them to "sneeze" and release a cloud of spores all around them.
Wanderer's can still kill with a single bite, but will only attack when provoked. They are attracted to sounds and use echolocation just like a Clicker. They are however the slowest of the infected (Due to their body falling apart or previous injury), they oftentimes stagger about croaking in pain.
Because they have large spore stalks on their back they can not be killed from behind with a shiv or strangled. The only way to remove their spore stalks is with the flamethrower or sustained gunfire (A shotgun blast will sometimes remove the stalks).
A Wanderer might stumble over to where Joel and Ellie are hiding and "sneeze" sending a small radius of spores all around, forcing Joel and Ellie to find another safe piece of cover.
The role of the Wanderer is to force the player to alter their tactics on the fly. It also makes players even more wary of their surroundings. A player can't just rush when their is a wanderer nearby else they risk stumbling into it or a cloud of spores.
There is a sad beauty in the Wanderer, finally it's tragic journey from human to infected ends. The human host body can finally pass and the cycle continues.