Aura build warlock is solid, not too many buttons, and if you wanted you could keep 1/2 paladin levels for the saves. Could do the same with Favored Soul, Cleric, or Sorcerer.
The main benefit of the Auralock is that with T5 Enlightened Spirit, you rely less on healing and more on hp (Which matters if you aren't able to spend a bunch of points in the racial tree for Reconstruct). The downside of Auralock (And Sorcerer) is that there's no medium armor option for warforged; if you take Adamantine Body (Which Bladeforged has racial tree support for), you have to fight around the spell failure. The aura from Enlightened Spirit isn't affected by spell failure, but the burst/blast are.
One build I've done 5? 6? times is 16 warlock/3 paladin/1 Fvs. It's not an endgame optimized build by any means, but it's pretty fun and a safe leveler. Can work as either a str base, or you can pick up cha to hit/dam if you have Feydark Illusionist.
16 lock for Enlightened Spirit T5, 3 paladin for hp/PRR defensive stance, and 1 Fvs for cheap Divine Might and the stacking light spellpower from Angel of Vengance (You could do basically the same with 1 level of cleric if you don't have Fvs). I'd pick up Maximize, Empower, Quicken, Improved Crit: Slash, then one of the Two-handed, Two-weapon, or Single-weapon fighting styles. I've done all three, all three have their ups and downs. For bladeforged, thf with greatswords is the obvious choice. You lose the +1/1 crit profile if you aren't using Vistani, but the melee is mostly for the hp+supplemental damage. Depending on your tomes/past lives/etc, I'd go cha based with Celestial pact for Soundburst, but str based with Fey pact would work well too.
You could also do an 18/2 Fvs/pal or 18/2 Cleric/Pal with Warpriest and greatswords. Fvs has the edge offensively if you go full cha base since they get innate cha to hit/damage, and they get wings earlier than a cleric can. Warforged Fvs was a hot build back in the day, bladeforged can just do it better. The only catch is that you might need to be in Mithral body and not Adamantine, at least if the wiki is correct (I seem to recall the 20% hp applying to all armor types, but I'd have to test it out). If you did cleric instead, 18/2 str build would work great in warpriest. Works as either standard cleric or Dark Apostate too.
Sorcerer would be pretty standard. Either go full cha caster, but with better saves, or you could do an EK build similar to the 18/2 cleric I just mentioned above.
Or, for something a bit different, you could mix around levels of pal/ftr/monk and do a kenesi build, possibly centered with greatswords. Several ways you could do that, depending on what splits you use.
Anyhow, just some ideas based on my experience. Happy to talk more about any of these ideas if they spark interest!