"you cannot add new heads (or body types for that matter)"
I can and I did it(body types https://imgur.com/GOrY9iG). Yes, they are not automatically selected when creating a new pawn(The game uses a standard set), BUT, they appeared in the game, they work and I can set them in the mod on the Character Editor.
I just added and renamed the textures and added these lines.
<BodyTypeDef>
<defName>Fat1</defName>
<headOffset>(0.09, 0.34)</headOffset>
<bodyNakedGraphicPath>Things/Pawn/Humanlike/Bodies/Naked_Fat1</bodyNakedGraphicPath>
<bodyDessicatedGraphicPath>Things/Pawn/Humanlike/Bodies/Dessicated/Dessicated_Male</bodyDessicatedGraphicPath>
</BodyTypeDef>
In this way, you can add as many bodies as you need, although you will have to choose them yourself, but this method works. And you can add as many hairs, as you need, just edit some lines.
Why is there no simple way to add a new type of head?
"There's a mod 'alien framework' which might let you do this"
I looked at the files in the Alien Framework and I do not know how / there is no easy way to add new types of heads.
I can and I did it(body types https://imgur.com/GOrY9iG). Yes, they are not automatically selected when creating a new pawn(The game uses a standard set), BUT, they appeared in the game, they work and I can set them in the mod on the Character Editor.
I just added and renamed the textures and added these lines.
<BodyTypeDef>
<defName>Fat1</defName>
<headOffset>(0.09, 0.34)</headOffset>
<bodyNakedGraphicPath>Things/Pawn/Humanlike/Bodies/Naked_Fat1</bodyNakedGraphicPath>
<bodyDessicatedGraphicPath>Things/Pawn/Humanlike/Bodies/Dessicated/Dessicated_Male</bodyDessicatedGraphicPath>
</BodyTypeDef>
In this way, you can add as many bodies as you need, although you will have to choose them yourself, but this method works. And you can add as many hairs, as you need, just edit some lines.
Why is there no simple way to add a new type of head?
"There's a mod 'alien framework' which might let you do this"
I looked at the files in the Alien Framework and I do not know how / there is no easy way to add new types of heads.