At this point the bigger gimmick would be to go the completely opposite direction. They could spin that as being new reader friendly too with some clever PR.
- Limited emphasis on crossovers, get the whole story in one book and not get scared away by casts of hundreds
- Continuity-heavy storylines, encourage new readers to stick with their books and watch their favorites grow and develop
- Point to DC's reliance on gimmicks and reboots as lazy storytelling, state that by contrast every Marvel story "matters" and that their writers can pull this off while DC's can't
- Long history should be a selling point not a turn-off, new readers are "jumping on" to a rich 50+ year tradition of great stories, all of which are conveniently available digitally
- Separate the franchises instead of combining them, emphasize the distinct flavors of the main books so that there's something for everyone to enjoy
- Make the universe seem bigger, not smaller, sell the fact that the Avengers movie is just the beginning and that the MU is huge and expansive with unique personalities in every corner, not just a handful of places with Wolverine happening to be in all of them at once
- Promote female/minority/LGBT heroes, make the point that Marvel's roster is just as diverse as its audience
The whole promotion could be titled "Marvel FOREVER!" or something like that, with the implication that once you buy one comic, you'll love it so much you'll keep coming back to Marvel, FOREVER!