If the monarch is the only person with the decision making authority, it can be abused far easier. Convincing a single person of the concept to do something abusive, is far easier than convincing a group. Especially, a group ideally made up of experienced Amtgarders. There is no way you can say a single entity with all the authority is less likely to abuse. This system offers a counter-balance to supreme authority, they still have the ability to propose and deny all candidates. All this does is disallow any one single person the ability to make a permanent change wihtout consultation.
If we make a knight that is a 'bad' knight, and release them to the Amtworld, then we have a shining example of our inadequacy as a kingdom to make important decisions. It is a condition, that once applied, is forever a black mark on our kingdom. Conversely, if we make few but no 'bad' knights, then we show that we are responsible enough to make proper decisions.
In Dragonspine, they are a static crown kingdom. They can know and become of aware of all the potential candidates. The see them week in and week out. The monarch has up-to-date first hand knowledge, and also has access to the DS-CoK at any time, in person. Now, in Westmarch, we are one of the largest states, and we encompass the majority of it. Even with concerted effort of the monarch, potential monarchs, and the knights, it is very logisitcally difficult to obtain the same level of awareness, communication, and peerage social pressure that makes this work for Dragonspine. I am not saying their system does not work for Dragonspine, it does. We will not be Dragonspine, we will be Westmarch. We must find what works for us. It may be that we need a system of what is done in DS, but then it also may not be for us.
When this system was discussed with the DS-CoK their were some on both sides of the discussion. So there is even room in DS for this option, but they may not need it, yet or ever. Point being, the way Amtgard works is culturally different in all areas of the country, there are variances to each kingdom, they all need to make it work the way they need it to work. If we do things the way most kingdoms do it, then we are guarenteed 'bad' knights, this is what history tells us. If we try something new, we just might find a way to stem that possibility. At the end of the day, Westmarch is its own unique thing, we can take from others to build a framework, but in the end we need to build our own house...errr, castle.