rms2003,
We are in the same situation. My employer has filed AOS based on EB, and we are going to file AOS based on my wife's DV visa, which is going to be current on November 1st.
I have done quite a lot research on how to get things in a risk-free way. I have talked to many, including KCC, USCIS, US consulates, attorneys here and my own attorney. It's a very long story but in short we have concluded to file another set of AOS based on DV visa and NOT to withdraw the EB-based pending AOS application.
I first wanted to figure out how to do AOS for DV, and talked to attorneys. Then, I called KCC for this, and the lady on phone told me that I didn't need to file another AOS application, I could get the already pending AOS used for DV. She insisted on this when I asked if she was sure on this. I told this my attorneys, and the attorney who filed EB AOS tried to get it confirmed. Although she said DOS had confirmed that, she could not reach anybody at USCIS to get this confirmed. After having tried many different channels to find out how to do this, she sent a letter to Nebraska Service Center to request the pending AOS be used for DV case about one month ago. However, we have not got any response yet, and we do not have much hope getting it converted into DV case timely.
We had considered Consular Processing, but we didn't want to go through CP process because of the security clearance risk. I went through security clearance 2 years ago while getting my H1 visa stamped, and it took 4 months not being able to return. My previous attorney had insisted that security clearance in immigrant visa cases would be completed before the GC interview and had advised me to go through CP. However, when I called the US consular in my country, the officer on the phone told me boldly NEVER COME if I went through NC in near past because I would not able to return. Contrary to what my attorney told me, she said NC may not be completed until interview, and for people like myself, it would not be complete 99%. No wonder, I am not working with that attorney anymore.
Finally, I have talked to at least five different attorneys, and all of them advised me file a new set of AOS applications based on my wife's DV and NOT to withdraw the pending EB-based ones. One of them told me that even if USCIS would convert the pending one to DV case, he would be concerned that it might not be timely.
I have hired a new attorney who looks like he knows this kind of cases. He is going to file new AOS tomorrow, and he said we would mention about the pending EB based AOS on cover letter. He said USCIS would either ask us to withdraw the other one at some point, or would relate these two cases and send the second application back to us, depending on the officer who process the case!