Most of 4th gen is a long way off from solo promotions happening. A lot of 3rd gen idols have just recently debuted solo, and there are quite a few who still have not. But still, just interested to see who you feel has the most star power in 4th gen to bring something interesting to the table. Not necessarily the ones who you think deserve to go solo, but you would be HYPE as hell if they got the opportunity. Just to see what they would come up with as far as song, concept, and style.
My top picks right now are Yeji, Winter, and Aisha. I feel like Yeji would come with something really powerful, Winter literally has the best voice of 4th gen hands down, and Aisha because....Aisha.