I've also been thinking about Mythic Blood recently. This was partially sparked by The Best and Worst Virtues thread, but also by the process of statting out a Verditius wand-maker, for whom I had not found a suitable Major Virtue.
Some additional effects that may be well-suited to the power:
- Imaginem effects: the first that comes to mind is invisibility for the character himself, but it could also apply to someone else. Creating illousions would also be great, as they don't need to penetrate in order to be effective. A broad MuIm that can adjust the caster's image so as to provide a variety of bonuses for social interactions (based on Aura of Rightful Authority and its variant from HoH:S) is also an interesting possibility. Something similar to the ReIm 30 Image from the Wizard Torn could also be of some interest.
- A ReAn effect might make the character a very good animal trainer/controller (see Commanding the Harnessed Beast, for example).
- Flying effects would be possible, either through ReAu or ReCo.
- In general, Intellego effects can be quite useful. You mentioned Vim, but others can be useful as well. Animal would allow him to speak to any beast, Herbam to speak to trees and plants. Corpus/Mentem to speak to the dead. Terram allows for a super-dowsing skill.
- A MuCo effect can make you into a shapeshifter.
- Teleportation effect though ReCo (whether you need requisites would depend on your saga).
- For the combat-oriented character, a damage effect in a variety of Forms is an option. It might not be worth much against higher-powered supernatural creatures, but as you could fast cast it without fatigue, it can be used to handle weaker creatures as well as mundane ones.
Just a few ideas that I've thrown together... 