I would not file incomplete packet. It will most likely be rejected and returned. You'd just lose time and money.
Maybe, just maybe, you can send AOS packet with I-864 filled by yourself for now. And maybe, instead of straight denying your case, USCIS will send NOID (Notice of Intent to Deny) or RFE (Request for Evidence). Usually they'll say they could not determine you were eligible to sponsor on your own and ask for joint sponsor. This can buy you some time. But there's huge risk involved and I would never recommend this. But is it better than filing late? Probably, is in my opinion. But there is a risk it may get denied and you will lose filing fees