"WELCOME TO THE LEGION:#When you build your force, choose one character of 50 points or less. That character gains the Legion of Super Heroes keyword and "wing symbol" this game. If your force includes other characters with this trait, you may increase the point value of your chosen character by 50 points if this character doesn't use this trait."

So...can I build a theme team with a 35 point Hal Jordan with this trait? Or is this subject to the same ruling on Gandalf/Nightwing?

Asking only because the wording is different. Gandalf/Nightwing say "as you reveal your force" and the Legion Founders say "when you build your force."

Thanks in advance.

Correct, Hal Jordan can join the Legion and it can be a theme team.

WttL goes into effect when you build your force, which is prior to the start of the game. Theme Teams are also checked prior to the start, as seen from the Rulebook:

THEMED TEAM BENEFITS
Prior to the beginning of the game, a force meeting the necessary criteria is determined to be a themed team.

These effects are both prior to the start of the game, so Keyword additions as you build your force will affect Theme Team determinations (as well as ATA prerequisites).

TL;DR - Yes, you can have 35 pt Hal Jordan in the Legion.

To piggyback, say I've got three characters with the Welcome to the Legion trait. Will multiple characters each get to designate a Legion inductee? Does it instead act as one trait collectively among them? Is it optional, letting me choose from A) three 50-point characters, B) one 100-point and one 50-point, or C) a single 150-point character? The thread about this trait and the Batcave asked this but I don't think it was answered.

It should be optional, 3 characters granting you your combinations A, B, or C.

I'm trying to figure out why you'd want to. Hal would get the wing symbol, so he couldn't be carried by most people. But... if you really need Gates to carry people 17 squares, I guess that would work.

I was just using Hal as an example.

It's a cheaper way than Earth Man to gain access to the Green Lantern Honor Guard ATA. 40 points < 103 points

I'd say yes to A and B but not C. But the way it's written:

...it looks like you can't use it to increase the points of the chosen character at all because the wording says "this character" has to not use the trait in order to get the bonus points. Trouble is, the OTHER characters also have the same "this character" phrase.

That glitch aside, though, there doesn't seem to be any language that indicates an increase for each other character with the trait. It only seems to care IF there are other characters with the trait.

This will need some clarification or errata to avoid problems ahead.

I would say option C would work just fine. I'm playing Cosmic Boy, Saturn Girl and Lightning Lad, all with that trait. I decide I choose Cosmic Boy to use his trait to welcome someone to the Legion. Saturn Girl has "If your force includes other characters (Cosmic Boy) with this trait, you may increase the point value of your chosen character by 50 points if this character (Saturn Girl) doesn't use this trait" so I increase Cosmic Boy's trait by 50. Lightning Lad has "If your force includes other characters (Cosmic Boy) with this trait, you may increase the point value of your chosen character by 50 points if this character (Lightning Lad) doesn't use this trait" so I increase Cosmic Boy's trait by 50 again.

My new member of the Legion was Laceration Lad (Arkham Asylum Inmate)