I'm glad you made this thread, Kuross.
Coming from a pure game mechanics standpoint, Immolation and other external "sacrifice" effects do not account for status effects/ailments. The only thing that matters in this case is whether or not the creature can be targeted by the spell in question. Thus, immaterial status plays a part in making a distinction between what I will call "external" and "internal" sacrifice effects.
An immaterial Virus cannot be targeted by external sacrifice effects. It
can, however, use its internal sacrificing skill, regardless of immaterial status. What this means regarding your original question is this:
creature skills are only able to be activated by the creature to which they belong. If the creature is in a state that prohibits the use of creature skills, it cannot use its skill, no matter the cost.
I believe the current state of sacrifice effects/skills is exactly how it should be, because it only makes sense that something like a frozen virus can't do what it does.