I never said amro takes all the alchemists. That is impossible and not neccessary. A.M.R.O only takes the talented, it just needs an army to maintain order.

Alchemy management and Restraint organization.

It means they maintain order in the world of alchemy, that means they oversee alchemy as well as the rogues. 

To put it simply you can use alchemy and not be in A.M.R.O, however you have to live under the constant scrutiny of A.M.R.O. If you don't break the rules, you will be okay. If you do A.M.R.O will come. 

There are certain exceptions. 

Now when A.M.R.O was still in its infancy merely a century old or so, it knew it would be very tough to bring order and control over the world of alchemy. Hence it took assistance from certain families. These families served to maintain order in those areas where A.M.R.O couldn't, however they too were under the scrutiny of A.M.R.O. It was a give and take relationship. 

The families would be able to get more freedom and A.M.R.O would get more intel from them and create more order. 

As time passed, over the centuries prominent bloodlines were formed, they are known as the 'newbloods'. Basically families that have been practicing alchemy for over 400 years. 

These newbloods maintain order at a lower level. Such making sure rogues in their areas are behaving, no one is being reckless etc. For this A.M.R.O tends to turn a blind eye to some of their illegal activities. 

However there is also a darker past as to the creation of the relationship between the newbloods and A.M.R.O.