With the unfortunate, but expected, end to Enhanced Experiences that opened the door to event based drops I think that there are ways that Event Based Drops could be implemented without the complexity that was E2.

In E2, Event Based Drops required the game to send metadata to Twitch, either directly from the client or from the game developers. Then a check would be made to see if a condition was met that would award a Drop. This meant that Twitch had to keep track of the metadata for every single channel and have more complicated Drops Campaigns for settings conditions (which may be limited in complexity).

An alternative, would be to have an Award Drops Entitlement endpoint that would require an App Access Token, with Client ID matching that of the game, with the required params entitlementid, and broadcasterid.

All handling of if conditions have been met to award a Drop could be entirely handled by the Game Devs, and not require Twitch to handle metadata. The only checks on Twitch's end would be to ensure that the entitlement id is valid, the broadcaster id is live and streaming the appropriate category (this check could be omitted, to easily allow for pre-arranged Drops while streaming a Special Event).

The awarding of Drops could be arbitrary and the devs could just browse random streams and throw Drops, but they could also have some complex system based on something happening in game, it would be entirely up to them how they wish to award them and to what channels. Campaign management would be significantly simplified compared to E2 as there's no handling of metadata or setting of conditions with Twitch. Privacy is maintained as it would still only apply to channels that have connected their accounts, and giving Drops to users is handled on Twitch's side so viewership isn't exposed until a user opts-in and claims the Drop (as is the case for time based Drops).

Another advantage to such a system is that it would also allow the Game Devs to integrate with any system they wish, for example in a game the streamer could open a chest, which then lets the players decide what's in it through an Extension or channel poll, and the result of that determines which Entitlement the Game Dev chooses to award. That's just one example of the freedom such a simplified Event Based Drops system would allow for, the possibilities are in the hands of the game devs.