Help Request - A Primaris Sized Plot Hole
I wrote myself into a corner. The chapter I've been working on has been lost in the Halo Stars for a long while and have branched off from their parent chapter. As someone that would like to play the game and not just write and paint, writing them to be pure firstborn isn't exactly an option. This gives me two problems. 1) The wider Imperium has no idea they are their own chapter at this point, they're simply missing and presumed dead part of their parent chapter and reinforcements would never have been issued to them. 2) Even if reinforcements were sent they'd have no way of reliably getting there. They do eventually find their way out via artifact, but that still leaves me with problem #1 and kinda wanted them to have the reinforcements before taking the risk.
The only solution I can think of is warp muckery sending primaris reinforcements meant for someone else and depositing them nearby where they can get added to the chapter. Warp shenanigans with time give me some space to play with integration if I am understanding the lore right. However, this has an interesting side effect of having a 1 in 9 (1 in 18? 20?) chance of the primaris being from the Lion's geneseed like they are. I did not intend on them being chimeric, but the possibility is intriguing now. By this point their numbers are dwindling and getting close to extinction and are 100% desperate enough to try it if it means extending the life of the chapter and thus extending the protection of the isolated human worlds in the region. It also raises the questions of who the reinforcements have the geneseed of and what the effects will be which might be fun. If I go that route I am partial to the Raven Guard, would there be lore problems there?
Other thoughts and solutions to this dilemma?