The Royal Marechaussee is 1/10th the size of the National Police Force and as you noted have quite specialized tasks. They are not the people handling day to day crime and interactions with civilians for mundane police actions. They also receive plenty of training related to the policing duties and are trained on how to police civilians. The national guard does not, and even MPs receive very different training and operate in a very different manner to the regular police.
This is very different than universally militarizing your police force across the nation or employing soldiers untrained in policing as police.
What do you believe the venn diagram of soldier and police skillsets looks like?
I think it looks like a normal venn diagram. Some things are similar and some different and it depends on what deployments or forces each has worked on. That's why NG troops are getting extra training in police duties and working together with normal police.
Police training academy is already generally considered to be insufficient, which is part of why cops continue to receive so much ongoing training as part of the job.
Getting a few rushed bootcamp style classes is not going to do anything to remotely bridge that gap.
This is very different than universally militarizing your police force across the nation or employing soldiers untrained in policing as police.
What do you believe the venn diagram of soldier and police skillsets looks like?