This theory is amazing. I totally support it. It's one the best I have ever read on One Piece. With it, you explain :
- what is All Blue and why nobody found it yet
- why Ancient Weapons were built in the first place
- why there was Joy Boy's excuse letter
- why Luffy will destroy Fishman Island
- why the manga is called One Piece
I think it doesn't have any hole. The reflexions some people shared also fit this pattern and add more sense to it because it shows there are two systems trying to develop and which have very different visions for the human being - Ancient Kingdom's and World Government's.
The idea that World Government is trying to create his own travel system makes that theory all the more plausible. Don't you think the opposition between Ancient Kingdom and World Government is simply the opposition between the sea and the land with two different philosophies behind them ?
Ancient Kingdom was trying to create All Blue so people can travel anywhere on their own with their own ship's rules whereas World Government is trying to create roads (like Roman Empire did) for people to travel so that they have to follow its rules and laws.
Ancient Kingdom wanted the sea to become the way for people to travel because the sea provides Freedom. You can travel anywhere without asking anybody - no kingdom or world government can take control of it and impose its laws, all the more than you use random travelling roads.
That's why Pirate King is not supposed to conquer anything - Luffy's words which pleased Rayleigh - but to be the person which the most freedom (travelling ability on the seas). Ancient Kingdom's fate and destiny was thus to create this complete free travelling system based on the seas thanks to the All Blue plan.
On the other hand, the 20 Kingdoms wanted to create check points between islands (All Bridges) so that the people travelling depend on them and have to obey their World Government. That means World Government likes the Calm Belt and Red Line who provide limited accesses to the 4 Blues and thus can be controlled. That's why there was a war between them: their goals were completely opposed.
I think the World Government has been building bridges in the 4 Blues since the end of the Void Century (Tequila Wolf is in East Blue). They did not do that in Grand Line because the seas are wild and storms would destroy everything. That's why the World Government wants to control the weather so that they can rule upon GL. That's also why the pirates are in GL, and especially in New World which has the craziest weathers and seas.
By the way, World Government is not only fighting against pirates because they may find One Piece but also because WG claims for the complete control of the travelling roads and pirates deny that. Even though they live outside the WG (New World), they have their own rules and don't obey the WG going wherever they want. So it's like refusing the World Government's fate which is to control everything with its rules.
All this means Luffy will likely have to fight against Dragon who is trying to conquer the land system. Dragon doesn't want to destroy the WG in itself but to change its principes. He wants the laws to be based on equality for all citizens and to erase privileges (Tenryubito and nobles). Dragon's fight is not against the land system: it's actually Revolution vs. Ancien Régime with a post-revolutionary world government whose fate is to rule the whole world.
Luffy's destiny to provide full freedom to people and establish free seas with All Blue will destroy the possibility of any world government, so it will clash with Dragon's dream which is to establish a world ruled by the principes of equality, which requires a World Government to impose equal laws. So Dragon and Luffy will have to fight if Dragon doesn't renounce on the post-revolutionary land system.