Right now, I'm favoring a 2 hour window with equally shared rewards for votes during that time window.

This is also an interesting approach and would benefit manual voters :) No need to wait 5 minutes any more and no arms race with bots regarding time.

The haircutting rule was created to reduce the maximum possible inflation during a decrease in Hive price.

Yes exactly, to further protect HBD (convert to HIVE) induced inflation, reducing the debt ratio from currently 10% to 2-3% for example would help during bear markets or sudden HIVE price decreases. A lower debt ratio would mean, less HBD in existence and less HBD converted to HIVE during bear markets.