@cardboard The solution seems pretty obvious - SP delagtors to tipu should get a higher compensation over SBD/STEEM depositors. Delegators are proving their commitment by locking in their investments with the 7 day cooling off penalty for withdrawing.
If you want the perk of instant withdrawals, then a lesser reward (percentage) would seem like a reasonable expectation for the system to ask of a user.
My .002 percent cents.