To be an effective top advisor, you need insight, intelligence, knowledge, empathy, and experience, not power. Those who believe Tobirama would be the best advisor failed. Tobirama grew up during the later years of the Warring States Era and the most turbulent years of the Hidden Village Era. He would have old and outdated advice for this current era. Orochimaru said it himself when he reanimated the first four Hokage. A lot of what Tobirama did during his days led to many problems down the line in the Leaf Village. He would not make a good top advisor. He would make for a great Head Ninja or Jōnin Commander, though.
If being a top advisor was based on power, then you would pretty much have a military state.