The only combined system seniority list at LCC is the Nicolau award. So, not only could the Nic be used, it is the only list available to use.
Also, the completely ironic thing about your question and DOH, is the only list that is actually in DOH order is the AWA seniority list. Both the east list and the AA list are not in DOH order, and the AA list is far from being in a DOH order. So, in an AA/LCC merger, seniority integration would happen based on the AA list and the Nic, and an individuals personal DOH would not be the driving factor of where they fell on the combined list.