I thought Simmons was kinda lame. He could've been used better but overall his obsession with Ada seemed pretty stupid and his idea of keeping order through terrorist attacks was just not a well thought out plot. I'm glad he died but at least he brought in The Family to the series (maybe Capcom will go somewhere with them). But now I think Capcom should bring in Alex Wesker. I'm curious to see the nature of his immortality.
I disagree with the weak usage of Simmons as plot device. The NSA chief seem more realistic than any other villains we've seen in the RE universe. Be it Spencer/Wesker/Alexia/etc. Using terror, and indirectly fear, to control the population is very easy to relate with regards to everyday life. People often use fear mongering to invoke others to take actions or express certain emotions. In terms of maintaining US hegemony, I don't see how what Simmons did any weaker than say Spencer trying to build a 'powerful' company called Umbrella.