There are two classes of conflict for this design: the easy, direct conflicts, in which Mordred goes straight at Arthur, and Arthur's options are straightforward, and the indirect conflicts in which Mordred works through other characters. The first class will be handled in plotpoints, but the second class is really the meat of the storyworld. I shall tackle the more difficult problem first.
Mordred's strategy will be to set in motion events that will lead to other characters confronting Arthur with discrediting challenges. The original LMD had a flawed example of this: the justice system. The basic concept was sound: set two characters against each other and then they force Arthur to choose between them. There are many instantiations of this principle, but the justice system had many flaws, most notably its clumsiness. I want to have a justice system in this version, but it has to be cleaner and more focussed on the interpersonal conflict. This is a subject for a future essay.
Romantic conflict is another rich vein to mine. Mordred wants to advance the public perception that Lancelot is cuckholding him, whether there is any basis in fact in this. There is also the possibility that Arthur himself may become romantically involved with others, and Mordred wants to advance this as far as possible to goad Guenevere into a retaliatory affair. Affairs between other characters are less significant, except perhaps as sources of conflict between them that can indirectly suck Arthur into more trouble.
Foreign affairs is another area for Mordred to exploit. He wants to exaggerate the Saxon threat, and make Arthur look indecisive in the face of that threat. If Arthur does respond to Saxon provocations, then Mordred will see to it that Arthur fails on the battlefield. In this sense, I suppose that the original design was sound, except that the recruitment of fighting partners was so damned tedious.
What about property conflicts? There are three forms of property: land, cattle, and objects. Land is not easily transferable; I doubt I'll do much with it. Cattle will be the primary transferable form of wealth. I'm not sure what to do with objects. I think that the property conflicts in the earlier LMD were off the mark. They seemed petty.
Which then leads me to the issue of retaliatory spirals. I suppose that they are useful inasmuch as Arthur will be forced to choose between taking early pre-emptive action or standing aloof.
I'd still like to see some other avenue for Mordred to pursue, and the Grail remains the one area of the legends that I have yet to incorporate into LMD. How can I fit together Mordred, the Grail, and my theme? One thing is certain: Arthur himself cannot seek the Grail. That is for another, a pure warrior. Hmm, what about this idea: Arthur is "king", Mordred is "black warrior", Lancelot is "flawed warrior", and Percival is "pure warrior"? Percival must find the Grail, but Arthur must somehow enable or motivate Percival to find the Grail.
Arthur must never fight. The king is no longer a warrior. Arthur was once a warrior, a great one, but now he is king. Lancelot was his warrior, but now Percival must become his warrior, and during the transition, Mordred will try to usurp Percival's place.
And all of this is really a metaphor for what happens inside the male mind.