You can be on leave of absense but you have to be on payroll
It is illigal not to inform INS. If you leave the company, the company will inform INS of your status when you left. You cannot hide from INS. But I think you can be on leave of absense, however you have to be in a position to show evidence of your employment (Paytubs & verification letter) if they ask you, which will happen 5-10% of the cases. In order to continue the processing, you have to be on job and I think salary cannot be less than the previous company salary(Verify with your lawyer). You have to file for AC21 through your new company in order to continue processing.