No, not like that. The way textures are handled are as followed:
Given a set transparency, the texture is applied to the skin.
THEN, you can alter the 'new' skin's transparency.
What I would like to see is that you can set the transparency of the texture itself, rather than only set the transparency of the resulting skin. Two different things. There are people like me who want to have certain skins have a certain amount of texture put on it, but without changing transparency.
In short, it's like this:
Skin + [Opacity x Texture] => Resulting Skin with Texture
Resulting Skin with Texture x Opacity => Final result
In the last line, that opacity can already be set. But the one from the first line, can not.
Other suggestion, while Im at it: Blending modes. Similar to Photoshop's layers, that you can set in which ways textures are filtered on the skin. Lighten only adds up the lighter parts of the texture for example, while screen has a multiplying effect of the former. Darken only adds up to the darker parts, and so on, and overlay rather multiplies both the light and dark parts, but leaves out the gray parts.