This has probably been mentionned somewhere before (I did notice a few posts for compilations by volumes), but here's my idea anyways:

For COMPLETED series
-maybe compile the whole series into one archive, while still leaving the individual chapters up for those who are simply looking for a few chapters.

For ONGOING series
- same idea, only group by volumes or simply by chunk for the much longer mangas (say chapters 1-25, 26-50, etc) and still keep the individual chapters.

These suggestions each pose their own challenges of course, but might help make the traffic on the site at least a little smoother (imho)...