Obviously, the Flood are not going to be implemented in the current game (This should be common knowledge by now, or at the very least, common sense) but, about those infection forms.....
I don't mean to sound condescending, but if I was playing a skirmish or multiplayer game in Halo Wars, having a bunch of infection forms at my command would be a game winner. The infection forms can infect organic targets (Marines, Elites) and immediately alter them into combat forms, which could then be used to eliminate additional enemies and use their bodies as fodder for more infection forms. The existing combat forms would then mutate into Carrier forms, which would then spew out additional Infection forms; the cycle continues until a massive legion of combat forms are mine to command, and with which to easily dispatch the rest of the opposition.
Given the frightening speed with which an entire planet can be infected with only a few infection forms, I would not discount the advantages of having a few of your own at your disposal.
"One single Flood spore can destroy a species"
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