They should have subscription model for back issues on a 6-12 month lag, and then sell the newer singles for $2 an issue digitally. Marvel's digital comics unlimited subscription service is pretty good, but it could be better. I think they currently add 100-125 new issues a month to the catalogue from a mixture of old and more recent runs. I would bump this to 150-175 issues a month, providing monthly updates to all ongoing series while continuing to digitize old 70s-00s stuff. They could raise the price slightly if they wanted. I'd pay $10 a month instead of $5 if I knew every marvel book would eventually be on there within a year. The few Marvel books I like reading and discussing day 1, I would still buy in digital singles. I would be buying more of these series if they were $2 a piece instead of $3-4.
It would be harder to do this sort of thing if your catalogue was creator owned like Image, but I am sure they could work it out.
Cross Gen had a digital subscription wayyy back. Years before Marvel ever did. All of their books were on there after 6 months or so. I read so many Cross gen books during the lifetime of that subscription. Granted they were only making $20-30 a year off of me (I don't remember the exact price, but I was a broke college student so it couldn't have been that high), but I would have paid $0 for Cross Gen books otherwise. I could barely afford the titles I was already following.