1) (G)-IDLE:
I love these ladies so much! I've been a fan of them immediately since their debut era but honestly didn't expect them to be this successful ngl lol. Talking about 2NE1, I think they show Korea and Asia can embrace weird and strong concepts, but your right they are usually 2nd place as we've seen twice now. For me my biggest problem I see is that they lack consistent ear-worm titles tracks. This may be heresy but tbh Soyeon is still a inexperience producer who struggles to produce songs that are repeat worthy consistently. The title songs from 2019 and omg were just...not exciting, good but not great n catchy. This makes them lack a era, where everything, charting, physicals, and digitals line up. (G)-IDLE hasn't left the the top 10 of idol ranking since last year, so the issue is not popularity but imo song choices. But hey being 2NE1 would be great! I actually think Soyeon, Yuqi, Soojin, and Miyeon have great personas that would attract the public or a certain segment, Cube just needs to give them more solo endeavors on the side. Soyeon= the rapper, producer, feature artist. Yuqi= the variety show it girl and China activities. Soojin= a it girl, could enter many fields. Miyeon= vocalist and actress.
2) ITZY:
ITZY hasn't fallen off but unlike lets say BP or TWICE they haven't gone from one major era to the next. Their debut is still I think their best performing song in SK. I think JYP needs to do two things; revamp their song choices, especially add real vocalization to their songs, end the talk-singing. DEBUT in Japan. Seriously I think ppl are underestimating ITZY, their very popular in SK and in Japan are just waiting to be a hit.
3) Aespa:
Idk. They could be the next NCT, Red Velvet or TWICE.
4) YGNGG:
I really don't know. Fandom is the huge reason why TREASURE is successfully, I don't think the GP is really into them. GG typically can't gain success off of fandom alone because their fans are usually a lot less. BP found a way to gain a huge fandom by the girls-every-girl-wants-to-be and tapping into entrenched pop culture archtypes like the Mean Girl, It Girl, Influencer, Pop Diva, etc etc established by US pop culture. The issue is that YGNGG won't get that demographic who already stan BP for obvious reasons and honestly the rest of the Kpop fandom seems already set against them. Idk about this group.
5) BHNGG:
They are the group I'm most sure that will succeeded. Given everything you said, they are the only GG I can see topping TWICE and yes BP in the first few years. The timing, agency, year, are ALL lined up. Big Hit just needs to choose the right concept and the right girls.
*Cube, what happened to that Westward advancement? That US debut will really propel them.