Thank you very much for your suggestion. I was unaware of MESH200 elements and had not considered changing element types. I was able to get the arc meshed with LMESH by converting MESH200 elements with keyopt(1)=2 into TARGE170 elements with shape LINE. Unexpectedly, the elements were converted into TARGE170 elements with shape TRIA when using MESH200 with keyopt(1)=3. I had expected this would result in TARGE170 elements with shape PARA. I am using EMODIF to convert the element type and it appears to control the shape automatically and ignores TSHAP. Thus, this method seems solve the issue for obtaining LINE shaped elements but not PARA.
I am interested in your view on the approach. Can you share any other ideas you may have for a different approach?