His idea was that the first account would exhaust 100% of its power before delegating it.

Extending the return time to 11 days solves the financial issue but could undermine usage of delegation. Who wants to tie up their power so long? Even 7 days is a lot.

My suggestions for a code fix is that:

1. you should not be able to delegate power that is drained - only unused power (this might come across to lenders as too rigid) and/or
2. power delegated in a drained state does not start to recharge until it returns back to you (this still doesn't seem fair that drained power magically and instantly recharges for use by the borrower) and/or
3. drained delegated power needs to recharge before it is usable by the borrower (NiCad Battery Model).

I like #3 the best as the most flexible, fair and logical solution. It might involve assigning a depletion /recharge state or clock to each unit/block/contract of power that is independent of lender/borrower. IRL if you loan me a depleted battery I need to recharge it to use it. Makes sense to me.

Wrote an article analyzing the various solutions here https://steemit.com/steemit/@cyberspace/proposed-steemit-fix-for-steem-power-delegation-self-voting-loophole