Hey, wasn't sure if this was a feature that I missed, but if not then consider this a humble idea/request.
If you've played around with Blueprints in Unreal Engine 4, you can double click node outputs to split them into component parts. So in the context of Pixel Composer in particular, you could split the "Surface out" output of many nodes into various useful parameters like position, scale, opacity, etc. which could then be plugged into other nodes.
That's a whale of a feature since it's very node-specific (or at least type-specific), so in the meantime you might be able to implement something similar by having a "get <parameter>" set of nodes for the more useful parameters. Say for example if you wanted to get the position of a 2D image node, you could input a Surface and it'd output a Vector2.
Just some ideas.