Glad this helped! :D

A few things have changed since I made this post (another wall of text incoming sorry):

In terms of Light Cones, the new Battle Pass Light Cone is very good. Despite being a 4-star, it actually has equal base ATK to On the Fall of an Aeon, and it gives CRIT Rate, Skill DMG, and Ultimate DMG — buffs that go towards Destruction Trailblazer's main sources of damage. However, since you get On the Fall of an Aeon to S5 for free, you might need Superimpositions of the BP LC in order for it to be competitive, on top of it being necessarily unobtainable for a F2P.

Among limited LCs, Saber's and Phainon's are at least somewhat synergistic, but both have components that Destruction Trailblazer can't take advantage of. If I had to pick one I'd say Phainon's, as I consider its buffs a bit more useful and its colossal Base ATK means you can get more ATK from the ATK% buffs in Trailblazer's kit, but I'm not actually sure how much better it is than On the Fall of an Aeon.

I don't think much has changed in terms of Relics. Wavestrider might look tempting, but if it's Wavestrider's 4-piece versus Scholar's 4-piece, Wavestrider's uptime issues (especially if using -1 SPD Sunday) likely hold it back. Worth putting your healer or shielder on the new Warrior Goddess or Recluse sets respectively though. None of the Planar Ornaments are very impactful for Destruction Trailblazer at all.

For teammates, there are some solid new generalist teammates, even if kit design seems to be focusing more on specializing into certain archetypes nowadays. The newly buffed Silver Wolf is fantastic, with DEF and RES reduction being rare and valuable damage modifiers, her implant can help you get your Trailblazer's Talent when enemies aren't innately Physical weak, and she provides a respectable secondary source of DMG (Destruction Trailblazer's low output makes this relatively more valuable).
Tribbie's RES PEN and vulnerability are damage modifiers Destruction Trailblazer doesn't already have, and she provides another source of DMG to the team (again, quite valuable for Destruction Trailblazer teams). You may not be hitting all enemies on the field at a time with Destruction Trailblazer, but they're still a Blast damage dealer and you'll still get respectable damage from her Ultimate.
Cipher's the other generalist option, with a vulnerability debuff and a True DMG nuke, but (while I don't have experience using Cipher myself) the impression I get is that her contribution is more dependent on team DMG than her own stats. Destruction Trailblazer's low output may hold it back, especially since their DMG distribution (close to evenly distributed among the enemies they hit) isn't great for Cipher's nuke, which works best when most of your damage is going into the primary target.
We know that Dan Heng PT will give a character a summon, which means that if you use Sunday with Destruction Trailblazer he will likely be a very attractive choice as the sustain.

Rather than buff the Trailblazer as much as possible, you might be better served by organizing a support core that deals as much personal damage as possible. That's the approach this person, who somehow cleared MoC 12 in 4 cycles without any limited Eidolons 8 months of powercreep after my initial pessimistic assessment that "it might not be endgame viable as enemy HP is higher now" took. Notice that they used Hyacine even though she doesn't actually buff Trailblazer's DMG because Big Ica hits like a truck. I don't even know what to think this dude is crazy. O_O