There's no issue from a naturalization standpoint with changing employers if AC21 applies. That's the whole point of AC21, facilitating job change. AC21 is eas

There's no issue from a naturalization standpoint with changing employers if AC21 applies. That's the whole point of AC21, facilitating job change. AC21 is easy, as long as the I-140 has been approved, the I-485 has been pending 6 months, and the new job is in the same or similar occupation as the sponsored job, the I-485J should get approved without any issue. Regarding maintaining H-1B status, it's a nice back-up but not all employers will support it - as long as the new employee has an EAD of course - although it's rare that a pending I-485 application isn't approved.