Outside of Invasion, you seldom get to play as an Elite in Halo: Reach. Adding the option to use your preferred species in Firefight instead of just Spartans would be a good way to remedy that problem, and it wouldn't be that hard to implement; playable Elites are already implemented in Firefight through Versus mode (which nobody plays) so it would be a simple matter of having the Elites spawn on the same team as the Spartans.
EDIT: Apparently some people are only reading the title before replying because this is the internet, so let me make it absolutely clear what I'm suggesting... I want Elites to be playable on the same team as the Spartans, fighting against the Covenant in Custom Firefight, not matchmaking.
EDIT: Apparently some people are only reading the title before replying because this is the internet, so let me make it absolutely clear what I'm suggesting... I want Elites to be playable on the same team as the Spartans, fighting against the Covenant in Custom Firefight, not matchmaking.