Thank you Joshua,
I like this a lot. It makes perfect sense to me. We used to do this in the old days before database sequences. Since this has to be an everyday problem, I thought I was missing something that had to be built into AGOL natively to solve it, but I guess I'm not. Note to Esri though. Support for attribute rules would be AWESOME, and a database sequence object would be appreciated. If it's there already and I'm missing it, please let me know and I apologize to Esri. Thank you again Joshua.