From what I understand, this series is airing in the summer, and I believe it's said that summer series in Japan are significantly shorter than, say, series that air in the spring. If this series is shorter than most Digimon series, then I guess I could see there not being many Digimon with human partners.
That summarizes everything I love about Masaru/Marcus in a nutshell. Well put, sir.
Not that I can recall. Even the earliest images of Tamers, Frontier and Savers showed at least three of the main protagonists. I have the same fear that all of the Digimon shown will be related to the one boy.