Agent smiths differ from the other Agents

[Metalogic]

Hell, if they wanted, they could shut down all of the life support and all of the young/weak would die quickly, and they wouldn't have to spend nearly as many resources on the wipe.

This is exactly Smith's interest. Provide a better solution to the cycle and get out of The Matrix. Who knows how it would've actually worked out for him but I think that was his intent.

I think programs are able to develop and become more self aware. If Smith was an Agent in the previous cycle, then maybe over time he was able to expand his programming like an exile expands their. When a program becomes an exile, they are no longer constricted by the machines programming. Maybe that's what happened to Smith, he became a quasi-exile. Maybe that's why he was chosen to balance out Neo.