One of the weak spots of the "Mar-Vell" run was the way that Marv's link to Earth, Rick, was almost totally surplus to requirements - I didn't dislike him you understand, but he had little going on in his personal life, and had no combat skills or advice for Mar-Vell. I would have a new character become linked to the Nega-Bands who would become Captain Marvel when he (or she) slammed them together, transforming into a super-human form and gaining a link to Mar-Vell's consciousness much like Rick had, only the new character would only see him when powered up. Mar-Vell would be there to provide advice in both hand-to-hand and tactics and strategies as he was a highly-trained Kree soldier/spy even before gaining the Nega-Bands and becoming a super-hero, but the new character would be in the driving seat.
A decent supporting cast would also be needed - some Earth-based and mundane, attached to the new character's life, while others would come from Mar-Vell's past and be more... extra-terrestrial in nature (Elysius, Mentor, Ronan).