Generally speaking, you can only be in one status as a time. If your wife is the A-2 principal and changes status to E-1 then you will also need to change to E-1 as her dependent spouse.
An E-1 visa is a treaty trader visa dealing with the importing and exporting of goods and/or services to and from the United States. Whether your wife is eligible will depend on the specific facts of your case. You need to discuss this with your the prospective employer's attorney.
While this answer is provided by a Florida Bar Certified Expert in Immigration and Nationality Law, it is for general information purposes only and an attorney/client relationship is neither intended nor created. You should seek out qualified counsel to review your case and provide you with advice specific to your situation. Review Mr. Devore's Avvo Profile for more information about his expertise in immigration law and how to contact him to discuss your case.
1. You only forefeit a visa when is E is approved
2. Depends on your application and sufficiency of provided docs