That is a good base to compare the karma donation proposal to.

Some differences in the proposal:

• The task posts are not specified to be in the main post area.
• The votes cost the voter karma - in terms of karma, they are zero sum.
• The votes can be worth more than 10 karma.
• The voter has to pick the vote value rather than use a fixed value.
• The vote value is limited by the voter's total karma.
• The votes are pre-committed to, after the task description is made but before the task is completed, and don't apply until it's completed.
• Down votes are not available.
• The example task descriptions are much shorter than typical posts.
• The system needs coding rather than using the existing code.

Not sure if I've missed anything major, some of those differences only occurred to me after I thought I'd finished (e.g. lack of down votes)