Field/Value Pins separation in Compositor Nodes

I've come to realise that we need the separated concept of field and value pins in compositor nodes as we have in geometry nodes. Right now AFAIK all pins in compositor are effectively field nodes (ie. the value they represent change on a per pixel basis, rather than being a single value applied to all incoming values of the node).

I show a use case in the shot above (an alpha to SDF converter), where if I wanted to make this node tree into a node group, I can't make the Distance values variable, because all node pins in compositor are fields, and fields don't make sense in those node parameters.