Like others have said, it doesn't matter how bad Lugia is perceived to be in Ubers.
With what you're going for, Lugia drops down to OU and takes the place of Politoed and Scizor as king of the OU tier. Lugia then becomes overcentralizing to standard play (yes, it most likely would happen, give that about 99% chance), then it gets put up for a suspect test where it will inevitably be moved back up to Ubers and the cycle would continue.
The one misconception that a lot of people have is that Ubers is essentially a banlist for the standard metagame (OU). There was a perception about Genesect being "too good for OU, but not good enough for Ubers." Did that stop it from going to Ubers? No.
Also, Smogon mentions Roost/Multiscale being an illegal combo on Lugia? It that because it is a banned combo, like DrizzleSwim, or is it just impossible to get both on Lugia? Cause I could swear I've seen ScaleRoost Dragonites, but figured I'd ask.
If it's an illegal combo, then Multiscale Lugia was released without Roost and he has no other way of learning it on his own... --- Krystal and Phoenix Wright for Smash 4! ... Please, Sakurai?
As someone who has reached #1 on fourteen different Übers ladders across Pokémon Showdown as well as four different Pokémon Online servers, I can safely say that Lugia is the fourth best Pokémon, and by far the single best wall in the entire game.
Read this post for more information: http://www.smogon.com/forums/showpost.php?p=4294206&postcount=13
Yes. Even though it's ranked 7 in usage and has been voted as best overall wall in Ubers it's terrible and should go to OU.
I hate saying this, but learn2play.
i wouldn't put any stock in uber usage stats lmao, the uber ladder is filled with scrubs. And best overall wall? There's nothing it has besides roost or recover that makes it a better wall than giratina.
Giratina's Dragon weakness and lack of Multiscale and Roost/Recover guarantees that it can never be as good a wall as Lugia. There is nothing besides the Water resistance and Rapid Spin immunity that Giratina has over Lugia. --- Smogon sucks.