This isn't a very good argument. Pretty much everything lags the game. The question is how much, and if it's too much for the majority of users.
This will of course be toggle-able if it would against all odds be implemented so there's no need to discuss that.
The way that blood works you'd never actually see the picture you made for it
It just doesn't work
Stuff like joints, arms, and head textures etc. work because they're a solid state of matter
Customizable liquid doesn't make sense and wouldn't work in practice
I honestly think the game has too much customization as it is