I would like to upload this image, which was uploaded as png, as a vector.

You can well delete it, but buyers would be unhappy if they would like to redownload again.

I can change the shape of the arms and the posture of the legs little by little, but I am worried about what I can do to achieve a large transformation that will satisfy Adobe.

 

By @? ??

You would need to make some modifications to this so that it will not be considered as spamming.

I hate to say that, but you could well colour it for the vector assets, or add a third group of individuals, one appears to be female, one appears to be male. You could also separate them into two assets: female silhouette and male silhouette.

You may have more possibilities, use your imagination. I would just not post the same asset again, as that may create confusion for buyers, searching for the asset in vectors and then buying the pixel asset. That would make them angry.