Welcome, scarletwing.
Unfortunately image deforming (aside from simple rotation and stretching) won't be officially supported until Spriter 2 is released (which will be a free upgrade for all Spriter Pro owners), but that's still at the very earliest I'd assume many months from now.
however, you might want to look at the great work by community member bwwd, who has put excellent use to the unfinished and unsupported experimental "skin-mode" feature already present in Spriter.
If I understand correctly, what he does is use skin mode to animated things such as hair and clothes, then renders those out from Spriter (having hidden all other sprites) and then replaces the skin-mode versions with standard Spriter sprites which use the image swap feature.
scarletwing reacted to Mike at BrashMonkey in Can I manipulate the image on Spriter ?