You surely can do that as long as the company that is filing for 485 is ok with it. 485 as mentioned in numerous discussions on this forum, is meant for future employment, thereby it allows the beneficiary to be off the payroll if the sponsorer is ok with it. Quite frankly, there are a lot of companies who would not encourage this, as they are on the losing side if they allow this.
There is always a chance that the candidate would bail out after 485 is filed and 6 months pass by, using the AC21 clause.
Hope this helps..