to be honest, i think Marik and Liao need a book more than Davion does. Davion is pretty much the posterchild for "standard inner sphere unit builds", they don't have many example of exotic lance concepts or even unconventional company/battalion level forces. the only one that comes to mind is the davion light guards' delta company (an almost battalion sized 'company' using lights) but ultimately that can be modeled using the light mech swarm rules from CM:Kurita.
but Marik has their 6 vehicle lances, and a tendancy to use combined arms/synergistic unit compositions at even company level. Liao was known for its 'dirty tricks' even during the succession wars.
further, Marik and Liao are the two that we have the least amount of actual detail on how they fight, because Davion and Steiner have gotten the bulk of the novels and sourcebooks in BT's history. Marik and Liao only really start getting viewpoint works (as anything other than 'mooks and villains') well after the clan invasion, when they've undergone a fairly massive cultural and military shift (gaining the WOB and undergoing Xin Shing respectively)
so at least in my opinion, Davion and Steiner should be the last combat manuals to come out for the inner sphere.
