As long as one of the enhancements lets me make the sword have a blue flame* that deals both fire and good damage to enemies, I'll be extremely happy with the Holy Avenger.
*A reference to Quest for Glory series of games, where the Paladin prestige let you obtain two longswords (only because you lose one of them as the plotline progresses) that flamed up with a blue flame of honor that deals fire damage to enemies, but can pierce the fire resistance that demons have.
Of course, Paladins in Quest for Glory are Neutral Good as opposed to Lawful Good - Doing what is right is more important than doing what is lawful.