When you said this, I was hoping you were referring to the lost potential with many live tiles, but apparently not.
While this does sound nice in theory, all it takes is one tiny mistake by a developer, amongst thousands of lines of code, to take it from a neat little battery monitor app, to a battery hog.
And in response to the HTC Clock app: HTC is an OEM, so they obviously get deep OS access when it comes to their programs. Anyways, that's only from one source, the risk for it becoming a hazard to battery life or otherwise is incredibly limited.