At least they'd focus more on education and less on wars...... That sounds good. Also, the worlds knowledge and discovery rate would sky rocket if science had the government behind it, as war and poverty would fall. I really can't think of a bad side to this, and it sounds pretty awesome actually. Work out the details, and I'd happily support this notion.
SScientists are the only group of people in any population that at least attempts to put facts oveemotions and opinions. Scientists try to provide evidence for any position they take on an issue and they actually test their claims, or anyone else's claims. Professionals in the field of science are the only people attempting to learn about reality and how to improve humanity's
Obviously people want a leader who bases policies on science and not on meaningless rhetoric. Unfortunately scientists will not fit this role, primarily because science is only concerned with understanding how processes work. In order to apply science to improve society, an engineer is needed. In addition, politicians are typically very good at communicating their ideas to a wide audience, while scientists do not universally have this skill.
As a nerd, I can safely say I'd rather have someone with actual social skills dictating policy. Scientists spend much of their time observing and testing, and administration would cut into that time, slowing R&D. In short, putting even more responsibility on our finest minds would be counterproductive. If the scientist wants to switch careers, then they should have someone with deep pockets willing to back them.