I have a Chapter of Space Marines, a Forge World (complete with its own force of Skitarii and Techpriests), an Imperial Knight House and an Astra Militarum regiment who are all aligned with each other and live in a single system. I've consulted with others and, as of yet, it is looking promising, being that while the Imperium doesn't often get along with itself, it can happen, and similar agendas tend to allow for cooperation anyway. There are several confirmed planets in the system: a Death World, where the Mechanicus and Marines train; a civilized planet where the Marines' fortress-monastery is; and the Forge World where the Mechanicus, Knights and Guard operate (also happens to be a starting-to-awaken Necron Tomb World).
The Marines hold something of a festival every year on the civilized world where they hold widespread recruitment. Under normal circumstances, only children 11-14 can sign up, but the plan is to have the Marines open recruitment to males up to 21 on this one day of the year. According to what research I've done, survival rate for adult males is lower when put through the gene-seed process, but it can still happen. The plan is essentially to have members of the Guard who operate in the system sign up on occasion and have several named characters in my army be ex-Guard.
I'm looking for opinions on this being possible in-universe.
Edit: I'm aware that there's a Space Marine-specific board for this, but it's sort of an Imperial Soup-controlled system as a whole.
Edited by Brother Liborio, 12 March 2019 - 01:18 AM.