Ghost attribute! New attribute to give to custom command made mobs.

Here is my reason I think this special attribute should be added to Minecraft.

A custom mob who needs to fly, shouldn't die when the mob they're flying on (a vex, bat etc) flies close to the ceiling suffocating the mob. I think an attribute called the ghost attribute should be added to Minecraft, it allows the mob to be inside a block without suffocating. It would be very useful for my command projects and the communities.

P.S. If there already is one, or, I have made a mistake please comment on this.