This is not a one-size-fits-all situation.
In some towns the local police can be lightly armed Peace Officers. But in places like Oakland, Baltimore, Chicago and New York they are outnumbered soldiers in a war zone.
This smells more like a standard Obama power grab - taking advantage of a crisis - than concern over the quality and suitability of local police departments.
Leftists like Obama and Hillary do not want power to reside anywhere other than the federal government.
First they dictated the size of our toilets, then came federal directives on the way our cars are built, then what we can do with mud puddles and ponds on our land, next was the strong arming of the school system, then federal control of our medical care, followed by forced homosexualization of the military, now comes the movement to intimidate, overpower and control local police forces.
And local police live, well, locally. A federal takeover, martial law, would need their cooperation. It won't do to have them able to defend where they live.
That's in every way the appropriate and Constitutional method.