Well I made something fairly close to what I was looking for. I built off of the DrumsUI loot window since that's what I've been happily using for some time (Thanks!)
The announce button does a beginchatinput which opens the channel with the starting DKP/Plat bid amounts, leaving the cursor open. You can then shift+click on the item to pop its link at the end of the line, then hit enter to send it. Unfortunately the only loot data accessible to the code is the display name, not the direct link, so this multi-step process is necessary.
To announce the winning bid one would first hover over the text of the item being assigned to put it in the 'item' box below(there doesn't seem to be any external way to reference the row data in the hardcoded itemlist elements that I could find), set the "groupmember" dropdown to the winning bidder, then with the value set to the winning bid either hit the DKP buy or Plat buy button to announce the winning bid before assigning it.
It's not really fancy, and the extra space it takes up persists even in non-leader loot (couldn't figure out an easy way to collapse the extra window space, scripted resizing didn't work) so I wouldn't recommend it unless you really want the extra announcement functionality.
I recommend going in and hardcoding the default DKP/Plat starting bid amounts to whatever you use, and setting the channel to whatever you use, either as "tc channelname" or "say" or "raidsay" or "gu" or wherever you want the default announcement to be.
I'm always happy if anyone wants to give any contructive criticism of my coding, or point out better ways of doing things. I don't promise to make any great efforts to improve it unless I want it improved; I mod because I'm lazy, not because I'm industrious.
Anybody else is more than welcome to use/hack to pieces any of the code I added (is marked with comment lines). My apologies to Drumstix if my adaptation is in any way bothersome.
