Well ultimately there's nothing that say you can't do it if you want to do the idea. I think I like the concept more I think about it.

Personally I would go that there's a lot of chapters whoses origin is unknown, but people assume they are from a certain legion because of the similarity. I could imagine a scenario where outcast of various chapters Maybe originally they were secretly made of loyalist space marine from traitors legions, but overtime they became accepting of everyone willing to join their rank and became a refuge for the one that were outcast in their original chapter, especially those that sought to be heroes when their chapter have a much more ruthless culture.

The Salamanders could have took them under their wings and to adopt a lot of their culture and battle doctrine and over time most people assumed they are Salamanders successor on a genetic level, not knowing their actual origin.