Even if it's a retroactive paradox, Gil has an item in his vault, not neccesarily similar, but superior to whatever thing you have. Also GoB is self-fueled when it comes to Prana, Gil just needs to give it a target.
Erm, what?
Do you have a source for this claim? Because he certainly doesn't have Excalibur or Avalon in the vault, or anything similar or superior to them.
Gil has something that does exactly what Excalibur does better, he just doesn't have Excalibur itself.
No he doesn't. And he doesn't have Avalon or anything better than it, either.
This is probably best not discussed here, though, because it could go on for some time. We have a general Q&A thread for such things.
This is literally the statement directly from CCC.
Also you are missing the point;
No, he does not have Excalibur or Avalon. He has, however, a similar object that's better at the same function (being the best holy sword/shooting kinetic beams of prana and dimension-hopping/omega regen respectively).
For an example used within the game itself, there's Karna's spear, Vasavi Shakti, a Divine Construct of the same magnitude as Excalibur and Avalon. Gil does not have Vasavi Shakti, but Gil without a doubt has a spear with the original version of Vasavi Shakti's function (killing immortals through the application of a Gaian concept of mortality).
Basically, presume that as long as it's been on earth and isn't bound by the rules of other celestial bodies, Gil has whatever your guy has, but better.
Once again, look up Plato's theory of forms. Using that as an example, Gil has the "perfect prototype" of whatever your guy has,
no matter what it is. This is why he even has FTL spaceships that can cross the entire universe in seconds; He has the "root of all human wisdom" (again, different from The Root), and one day Nasu!Humans will build such a ship, so therefor Gil naturally has it.
I honestly dont give a shit if you find it unbelievable or implausible, Gil having everything ever has been established by CCC and confirmed by Word of God, no matter how special snowflake Satoshi is, Gil has anything he has and better. If lantz doesn't want that to be a thing, then he should write original fiction with Satoshi instead of relying upon the rules of the Nasuverse.