I was creating a character when a thought occurred to me. I have a razmirian priest sorcerer who uses a robe of arcane heritage with a Rakshasa bloodline. His archetype replaces his nondetection ability, while his robes enhance his bloodline abilities up 4 levels. So a 5th level razmirian priest with robes of arcane heritage would.....
A) gain the nondetection ability only when wearing the robes and gain his archetype ability only at 9th level.
Or
B) gain the archetype ability.
Neither.
The general rule is that archetypes replace abilities. A character does not gain access to the replaced ability. The replaced ability (False Channel?) does not say it is itself a "bloodline ability" so the robe would not grant access to it.
That said, you could probably convince your GM that the replacement ability is itself a bloodline ability so that it does work, though I don't believe that by RAW it works this way.
However if your character took Eldrich Heritage feat to gain a bloodline ability, the robe of arcane heritage would increase the power of that granted bloodline ability.