From my perspective, packs will work best with large trackers that have other content as well. These packs work well because they will get consistently snatched (because of the large userbase, there will always be someone wanting to catch up on 'X' show) so there will always be seeders and there will always be motivation to keep seeding, and if they are freeleech there's the added incentive of free and consistent upload for keeping them seeded, which can be translated to downloading the general content of the tracker. The ratio imbalance of these packs can be offset by uploaders and ranks which can only be attained by seedbox whoring.
Is there a point or purpose in creating a small community that seeds only packs (which can sometimes be massive)? Where is the motivation? If I understand what Packme.in is, than it sounds insanely and entirely impractical. In order to match larger sites that use packs as a perk you would have to ask tons more out of your userbase, or you'd have to use alot of resources. I don't see much sense in the concept of your site. Perhaps I'm missing something.. if so enlighten me?