Though we don't have any news about allowing third-party interface addons, we'd definitely be interested to hear what functionality you feel is important to add to the current UI. Others have offered a few suggestions (thanks!), and it's helpful to us if you describe what you think is missing and let us know what we can do to improve the UI!
if you can get a resize on buff/debuff, and filter by debuffs applied by you (try raiding with 4 arsenal bounty hunters, and being able to tell which debuff is yours, when the debuff is tiny, on a boss with 4 rows of debuffs, is tough), and then which debuffs can be dispelled by you, would make a HUGE difference. IMO.
i don't think i'm alone in my personal opinion either.
edit for bullet type for ease of reading:
- Ability to size the buff/debuff INDEPENDENT of the target frame - I don't want the target frame to take up half of the screen to be able to see a debuff clearly
- ability to MOVE the buffs and debuff independent of each other - example, buffs on top, debuffs on bottom
- ability to filter out all other debuffs, except those applied by you
- ability to filter out all other debuffs, except those that can be dispelled by you