Even the project being the virus at all is something that we only infer. It is something that fits, that does not make it a proven fact.
I did write "presumably" in the original post.
Fortenium is an object, solar/atomic refer to processes.
True, although we have no source stating that Zero runs on anything else than standard fuels for a standard solar/atomic generator. His "unknown power" lies concealed by mysterious facets of his design that defy traditional analysis.
Zero's power source is not Fortenium, this is true, but Fortenium is relevant to the discovery of whatever does power Zero. Bass has been tied to many things, including to some degree emotion and heart, but energy life forms aren't one of them.
As I mentioned before, that scene presents several ideas at once:
1) Wily dislikes Forte's disobedience and regrets creating him.
2) Currently Fortenium is the strongest energy on Earth, but that's not for long. Wily learned from the accident that made Forte and Fortenium.
3) Wily created a new type of robot with a far superior power level. It's not yet complete. It's also much more than just a simple robot.
These points hold the following implications:
1) Wily will do anything in his power to avoid another disobedient robot. This is however exactly what Zero turned out to be prior to correction by the Sigma Virus.
2) An energy that exceeds Fortenium does not yet exist. It's a hypothetical, a concept. The Alien Energy at the forefront of Power Fighters' plot is thereby weaker than Fortenium. This new energy still needs to go through the many uncertain stages of research and development. Despite this, Wily has complete confidence in Zero's design. This time it won't be an accidental creation.
3) Wily clearly highlights the technical complexity of Zero's design. The exact specifics of his systems are known only to Wily. Other than him, Sigma has the greatest understanding of these secrets.---Sigma: I met an old man who knows a lot about you... He told me an interesting story. He told me that you are something far greater than what you appear to be... On his advice, I scattered the Virus so that it could infiltrate you, but you haven't shown any signs of waking up...
---Zero: I won't become a Maverick! I won't yield to your pitiful virus!
---Sigma: Hee hee hee. You don't seem to understand. I'm not talking about becoming a Maverick. You felt it, didn't you. You felt a tremendous power fill your body... A power from the Virus. That is because the Virus purifies your body.
You may doubt Sigma's words, but he's actually correct in his assessment. Zero, who was once an irregular, won't become an irregular from the infection (ZERO Collection timeline). Thereby, power comes from the virus. The virus purifies his body. Zero's greatest level of strength comes from contact with the subspecies of a virus Wily created at least two whole games after Power Fighters.
My main shpiel is that while the virus certainly serves to draw tremendous power from Zero, I do not believe that Zero requires it to overpower Bass.
Yes, default Zero overpowers Forte, but so too does default RockmanX (and the combat Repliroids of 21XX).
Neither "the strongest energy" and "Limitless Potential" factor into this equation. As I see it, Forte mimics Rockman, Zero and X do not. By raw specs alone, they are superior to a dated design powered by Fortenium. Their "unknown power" of unanalyzable mystery only serves to completely topple the scales.