Yes.   Have ran into the same scenario and you can create an identifer that only applies to the AIX server class (or whatever class you are trying to control) and put it in the order above the hardware class identifiers.     You do not need to revise the OOB identifier for Serial Numbers.     There is one value you have to change on your New Identifier so it doesn't go to the remaining identifiers.   See this article for assistance.   https://community.servicenow.com/message/680308#680308

What we did was copied the code from the Name/Class identifier into a new identifier.   The new identifier only applies against the one table "AIX servers".   Make sure to change the line from "false" to "true":     return new CIIdentifierResult(matching, matchable, true).   This prevents the AIX servers from going to the next identifier for matching serial numbers or any of the other identifiers in the list.

Please let me know if you have any questions.