I don't know how it could be transfered with post/comment payout because when users click on the Tip button they will sign the transaction. I think what you suggest would be more complex, not even sure how you would do it actually.
In my idea, the vote transaction (with nonzero tip option) would immediately deduct the tip amount from the voters account and add it to the pending tip balance for the post/comment. Upon payout, the tip balance on the post/comment would be added to the reward balance and paid to the author.
I see what you mean but I don't understand why you would want to add the tip amount to the post payout and delay the tip reward when it seem like it would be easier to send the tip immediately.
I've spoken with @ekitcho and he is working on a tip button which may require users to enter their private key every time they want to tip. This is never gonna work, as I said in my post the only way this feature could be successfull is if tipping is a one click process, basically the same as when you click "like" on busy. Even the upvote action on steemit is not 1 click,it's a 2 step process, the 2nd step is asking you to adjust SP meter.
To make it a 1 step process, an additional wallet would have to be created where funds could be spent with the posting key. As we've talked about on bitcointalk. @Ekitcho didn't really know whether it was technically feasable or not so maybe you two should probably get in touch to discuss this matter further, the busy team want to add this feature but they need to make it the right way or no one will use it!
Yes, having a separate "tip jar"-wallet would probably be better.