I’ve been thinking and compiling knowledge from the comics that could apply to Young Justice. I know the show has not and will not follow the comics exactly, but most of the characters are somewhat the same; just some of the details are different.
With that said, here goes. SPOILERS could be ahead. Some of this you guys have already assumed on your own, or maybe all of it. I'm going to assume you haven't.
Impulse is from the future, and he could have access to knowledge about the past (more than just secret identities, like he has already shown). Jaime seems to be very important in the grand scheme of things, since the storyline in tie-in comic issues 20-25 details his recruitment. On top of that, he has had a prominent role in 4/9 episodes in Invasion. Impulse now wants to be friends with Blue Beetle, and with that knowledge from the future, this could be part of Impulse’s grand plan to save the future.
Here’s where the potential SPOILERS could start.
I’m 99% positive that the Reach is the Partner. In the comic-con trailer over the summer, we saw someone that I assume is Black Beetle confronting Static, who is one of the kidnapped runaways. Meaning that he is present wherever the Team is going to rescue Lagoon Boy and company, trying to stop them. In the preview for next week, we see Blue Beetle confronting Black Beetle, so his reveal has to be tied into the rescue mission.
For some comics background, Black Beetle is a bounty hunter from the future. The Reach (in “Bloodlines”) have been saying terms that Impulse has been saying, like “the mode” and “crash.” These are presumably slang words from the future. I’m going to conclude that the Reach invading Earth are from the future, and maybe they hired Black Beetle as a mercernary to protect them as they tried to elicit the metagene.
How this ties into the Light or the trial on Rimbor, you may ask? Perhaps Vandal Savage has run into the Reach before in ancient times (like that temple we saw in "Beneath," which the Light is obviously interested in), and he was promised they would return. Perhaps Savage used the Justice League to attack Rimbor in order to get them to return, and during the trial, the earth would be seriously unprotected with so many from the League gone. The Reach then came back from the future during this optimal time period in order to find the metagene. Perhaps this was what Savage wanted in the first place: to isolate the metagene to help evolve humanity, using aliens from the stars and the future to help him achieve it. The "destruction" of the world could lead to a new age (akin to the plan in Justice League: Doom).
Impulse knew Neutron from the future. Neutron was experimented on by the Reach to activate his latent metagene, but the process was unstable. Maybe he knew the Reach were responsible, or learned later, and that was the real reason he sent Impulse back in time. To impede the Reach from their search, which would in turn stop Savage from helping humanity evolve by destroying the world. Maybe he used perfect conditions to end the world and then to activate the metagene across the globe.
I don’t know why, but all this seems oddly possible. It ties the Light, Impulse’s future, the prevalence of Blue Beetle, and the Reach looking for the metagene together. I’m fairly certain that Impulse was looking for Blue Beetle, even asked for him by name, in the very moment he arrived from the future, but I could be mistaken. Blue Beetle is definitely key to all this. To this whole season. The infiltration of the Light by Artemis and Aqualad is not even the important part to me; Impulse's quest to stop the ruination of the future is the main plotline of the season.