It's a good idea, but the current display is too vague. Unless you read this post, it's not clear what the number means.
To be honest, I'm not sure about any way to display this that doesn't require reading about this feature first. I think it'd be better to change how morphing works (just require the change in resource if the change is positive; if the change is negative, give it after the morph). I can't think of any way that this would cause issues and it seems more logical.