The president has a large degree of control over the agencies and their output, so in practice agency delegation granted presidents immense power. This power went largely unexercised due to norms. But that has been slowly changing, and under Trump radically changing. And if SCOTUS adopts the Unitary Executive Theory, as they seem poised to do, then we'll have something very close to a king, difficult to distinguish from 18th century Great Britain.

I don't see how requiring Congressional ratification for rule changes would grant the president more power than he has now. Currently the primary checks are procedural limitations; but were Trump a better, more well organized leader these procedural checks wouldn't pose much of a hurdle at all.

If you want a more technocratic administrative state, the agencies would require more autonomy from the president than they have now, but things are moving in the opposite direction both as a practical matter and constitutionally.