it is possible that a chapter will split and one part of the split will go to cadia or armaggedon, actuallyive written the background of my tt space main chapter and due to the lack of members they ahd they recruited from armaggedon.
And don't the cadians have the best IG?... Also why don't they use the Kasrkins to create new space marines?...
Kasrkin, i.e. stormtroopers for non cadians are generally too old to undergo marine training and the enhancements. They basically receive the same training in the schola progenium as sisters of battle do. Technically they are on par with them, but do not get power armor.