In asking this question I assume a few things and I should make these assumptions clear:
(1) GMark uses the term Christos as a category for Jesus. Furthermore, it seems clear that one of GMark's unfolding plot lines involves revealing and demonstrating what this means.
(2) Some form of the parallelism represented by Romans 1:3-4 was in circulation prior to Mark's composition. I.e. some folks in the early Church were meditating on Jesus' significance in similar language/titles that we find in GMark.
(3) It is almost impossible not to view these titles (Christ; Son of God; Lord) and language (death and resurrection) without using the theological categories of a much later Christian period.
Points one and two suggest that GMark exists in a world of theological categories and that something like "Christology" was already unfolding. Point three suggests that if indeed Christology (or a like category) was a concern of GMark, it was a category under construction as opposed to something that was doctrinally stable.
Of course NT scholars have been using the term "messianism" for sometime now. Part of the reason for this is to sidestep some of the problems of anachronism. But in my experience, the category of "messianism" can bring the same Christological assumptions to the text.
So I am curious to hear your thoughts: is "Christology" the wrong category by which to measure Mark's Gospel?