I would definitely not allow improving Presence through Corpus.
A hideous mercenary captain with an ugly-as-hell face and an intimidating reputation of violence and courage shouts his men into battle through the use of his charisma and fear-inducing. He has an "Ugly" Flaw and a high Presence.
A beautiful yet shy young mendicant monk in the service of an older, more experienced monk, can't bear himself to talk to that seductive dark-haired woman, or deal with the insidious chaplain that orders him around when his master is away. He has a "Venus Blessing" Virtue and a low Presence.
I'd definitely allow Corpus magic to make a character more physically attractive. It's just that I wouldn't translate that into a higher Presence, but rather some other, Virtue-like effect.
Of course, YSMV. Sometimes characteristics' interpretations can be rather SG-dependant.
I understand what you are saying, but at the same time, the question is not whether presence is appearance dependent, but whether it can be approved through appearance. The ugly captain's presence might well benefit from a more "ennobled" appearance despite the fact he has a high presence without it. Similarly the shy and attractive young man might find himself less shy- or at least more effective if he overcomes his shyness- if he were still more attractive. I'm not trying to argue that there is no mental component, merely that there is also a physical one.
You make a fine point about that. But I still think it's worth noting that Presence is not only about being physically beautiful, as it can also mean you're comanding, intimidating, etc. Yet your point still stand that, even if Presence doesn't necessarily mean good looks, it might benefit from them. I guess it's a matter of making a judgement call by the SG/Troupe, so it might be dependant on what the Troupe thinks is more reasonable. I would still not allow increasing Presence through Co, personally, but I would allow an effect that would give bonuses to some Presence-based rolls.
Aura of Ennobled Presence grants a bonus due to a bunch of appearance-related changes. These changes include alterations to the image that could be done via Corpus (better posture, better skin condition) and others that are not (better lighting, better clothing). This translates into a bonus to social roles in specific circumstances.
So yes, I am totally fine with the idea that you can make some corpus changes that will provide a modifier to social rolls in specific circumstances. This does not, however, translate to an improved presence.
Not sure how physical appearance would factor into Certamen, but Presence absolutely (and sensibly) does.