The definition of mixed Hodge complexes by Saito is a very interesting one, since it's more a cohomology theoretic than geometric generalization of Hodge structures. Since Saito's motivation for mixed Hodge complexes comes from simplicial schemes, as standard mixed Hodge modules become useless for them. This brings us to the question of cohomology, since the definition of mixed Hodge complexes is uses a very category theoretic language.
Question 1: Could mixed Hodge complexes be used to generalize current cohomology theories? (especially de Rham and Deligne cohomologies)
Question 2: Could mixed Hodge complexes be used to construct new cohomology theories?