Depending on the time period, SOG is still running Shining Brass, and getting more blatant about the air campaign in Laos. Could also play an LDNN or Montagnard Mike Force advisor in addition to one of the RT's.

I'm not sure that Vietnam was ever a 'fair' fight in terms of firepower parity, but it was a very frustrating fight in that the enemy dictated the operational tempo in many cases. But if you're looking for a different perspective, I'd argue for the early 1960's before the US massively deployed combat troops there. You had a very different war where the capability of the enemy led to that deployment in the first place.

I'm good with whatever path it takes though.