On the HUD: Yes, that's certainly possible. The target's health/power would be percentages only rather than full numbers, but it's doable. The ProxyActor window (which controls the health/power bars above each actor's head) could be modified, or a window could be created that's fixed at the center of the screen with 30% opacity.
On the group window: Maybe...
http://www.eq2interface.com/forums/s...ead.php?t=3908
Most of the groupmember dynamicdata tags never worked, not sure whether or not that one ever did. It might be that the gauge ones worked, just the text ones did not. I'll have to check that out.