Just make your army a successor chapter. I keep mine, relatively, generic; skeleton space marines with steel and silver armour with red shoulder pads (or where ever their iconography would go). I use the "Emperor's Immortal Swords" as Crimson fists, Ultramarine, or blood angels (depending on my mood and insanity).
I made a mistake with my first batch of marines, making them heavily Dark Angels; I could barely use them as another SM force (once the DA codex started to get to old).