One concern I would have with this suggestion involves those cases where a mod supports more than one version of a game.
Here are a few different instances to consider:
1) A mod is not affected by game version changes. Should the author continually retest/update the version listing as new versions of the game are released? If so, how would players who choose to stay on a previous version of the game know that the mod would work with their (older) version?
2) A mod requires updates for some new game versions, which would require them to create a whole new mod listing for each game version they intend to support. As it is, I think most authors simply offer different sets of files and advise users to download the one that matches the game version they have installed.
While I can understand that such a feature may be useful in some cases, it could present more problems in other situations.
Well, technically, yes. That is the correct course of action when distributing any product, you need to be exact.
Still, they can always write in the description something along the lines of:
"My mod has been tested, and is compatible from version 0.45, to version 1.21"
Which is highly unlikely, mods break in every version, but is still a possibility.
If the players want to stay in an older version of the game, this checkbox makes makes it so much easier for them to find the correct version of the mod for their game.
The listing stays as is, I never said nexus needs a redesign. In each file you'd have the correct game version compatibility box, a stamp of approval from the mod author themselves.
I don't see any problem other than, that the mods already in the nexus will all become "unverified". But you'd still be able to download, and play. They won't get banned, or deleted.