So, this is a little expansion on the idea behind the first idea of this site.
A problem that first idea had was the selection of the games: when I wrote it that first time, in the Game Career Guide, I knew nothing about Metal Gear Solid V. But now, I can change the original idea a little bit, to make this proposal, Lego Metal Gear Solid, the story of Big Boss.
Taking out Metal Gear Solid 4, and adding Metal Gear Solid V, keeping the continuity of the series in a single game, there are a lot of small connections that can be made: soldiers you recruited in Peace Walker may appear on Phantom Pain, your Mother Base will be exactly the same in both games, when needed, bringing the idea that this is “your” Mother Base further than Phantom Pain has done.
About the game itself, however, I wouldn’t do it as an open-world game. The people behind Phantom Pain had their reasons, and the game is amazing, but I prefer a smaller approach than an entire world to be explored: I would take all the missions that are not fundamental to the plot, and create stages, similar to how they did it with Ground Zeroes, and then let the player have their fun, with their AI partners, or the online cooperative, fulfilling certain objectives in the right order. Then you could go back to it, exploring it with characters that have special skills, like a better vision, or that may unlock special doors.
The only problem I see with Phantom Pain, as a Lego game, is the tone of it. They tried to do a revenge story, with a dark character, but that felt, to me, a little flat. There would be changes in this game, to allow it to be played by older kids and teenagers: instead of killing your soldiers that were contaminated by the vocal cords parasites, they would be cured and sent to a hospital somewhere, at same time showing why they can’t be with you anymore, and still keeping the idea that they were in a serious risk. The characters would also be a little bit changed, to make them more cartoon-like – Skullface would deliver more cheesy lines, while Huey would be more like a mustache twirling villain, making it feel a little bit less serious and more light hearted.