It has already been requested to be able to make database entries as child/parent items. This is currently not available and some special consideration would have to be made concerning digital games... such as the fact people can buy digital DLC for physical games. You may not think of it that way, but if say the PS4 acted like VGC, then if you add a physical game, you also would get the digital game added and then the DLC. Currently collectors typically will not add *both* a physical and the digital equivalent to their VGC collection for those types of hardware.
You'd have to resolve this by reformatting the site a bit. Right now, there's a standalone listing for every individual item, so when you do a search, you have to wade through all the various permutations. A better approach would be to have a master entry for each game, with sub-entries for each platform, and DLC specified as children attached to each sub-entry that are freely assignable to both digital and physical. So for example:
Master Entry - Alien: Isolation
Sub-Entries:
- PC/Steam
- PS4
- PS4/PSN
DLC Entries:
- Last Survivor (PC) (no format needed unless there are both physical and digital)
- Last Survivor (PS4) (no format needed unless there are both physical and digital)
Painstaking, but it would have the added bonus of cleaning up search results quite a bit. No more hunting and pecking around for whatever platform, and it gets really dodgy if it's something with numerous re-releases. It would also eliminate stuff like Nintendo Network being its own primary platform category.