I don't think a 1/2" is gonna mess with the drive angles enough to cause an issue. Welding a plate to the oil pan is stupid, welding it would weaken the metal. Skid plates sit under the pan so that it takes the impact before it gets to the pan, that would be more effective for protecting the pan. But he said he is going to run the stock suspension so the 1/2" should make it safe to not have anything.
"I knew a guy who bought a used car through a newspaper. Ten years later...bam...Herpes."