I'm looking for same thing, digital would be nice, surprisingly there are no digital clock apps in the store. None that I could find anyways. None worth downloading.
Unless you own an HTC device, a "live tile clock" is useless as tiles update at minimum every 30 minute intervals. Besides you already have a system clock at the top right corner.
My guess is that restrictions let the company predict the performance of the phone and I guess make the verification process quicker. I mean on android there are some apps and widgets that reduce the performance of the phone and Microsoft probably didn't want that to happen on their phone's OS.
u can sideload Time:Me app and disable weather and battery from that for u to display the clock alone. Find the link to sideload version at windows phone app desc after searching for Time:ME