so sorry to hear this.
I have been using poloniex for a long time and have allways had good experience with both the exchange and the dev.
The only right thing to do is to take 12,3% from all users and repay later.
Raising the fee temporary and/or a share system (like cryptostocks) would be a good approach to get the btc to pay users back faster.
Looking forward to trading at poloniex again!