Some time ago, I wrote a paper with a coathor, who is the head of the lab I am currently working at and, essentially, my boss. We sent the paper to one of the best journals in our field, got overall positive reviews, revised the paper, and recently the paper was accepted for publication.
My lab got a substantial funding this year and my coauthor wants to include the funding information into our paper. However, there is a complication. The acceptance date of the paper is earlier than the date when we recieved the funding. As a result, the paper will not be accepted by the funder (we asked the funder about that). My coauthor decided that we should do something to change the acceptance date. We asked the journal about it, and the journal replied that the acceptance date, basically, cannot be altered. The only way to alter the acceptance date is to withdraw the paper on the basis that we have found some crucial mistake in our findings, then resubmit a revised version of the paper and undergo a new round of peer-review, which, I am afraid, might take a long time (it usually takes at least a year for this journal to make a decision). My coauthor insists that we should try to do that and he even asked me to try to find some flaws in our paper or something that can be improved in such a way that the need for improvement can be justified.
Frankly, I feel dishonest, weird and even somewhat dirty for being involved in this situation. I want to publish the paper as it is, without including the new funding information and altering the acceptance date. Moreover, I find the whole matter somewhat unethical.
I told my coauthor about my concerns and my opinion that it is reasonable to not include the new funding source. But he wouldn't listen. What's worse, is that I am the corresponding author and I have to negotiate all the matters with the journal.
I'm not really asking for advice. I just want to know your opinion about the situation.
Edit: I would like to thank everybody for the comments. Your feedback was very helpful to me. I managed to persuade my coauthor to change his mind and do the right thing.