A system similar to what Steam has: Trading Cards that can be unlocked by engaging with the streamer. (Requires the streamer to have such feature enabled; The streamer can design and upload their cards and set conditions such as drop rate, how to get them, say by following, subscribing, donating etc.)
Each user would have their own trading card menu in their personal dashboard, to check which have been unlocked, from which streamers, etc.
Viewers can also trade cards with others if they have doubles, etc.
Collecting all cards from a streamer could also unlock a badge or whatever the streamer decides the compensation is (say access to all channel emotes without the need to subscribe, for example).
I am use on this moment via https://app.streamheroes.gg/streamer/twitchtvfalcons
Same Idea you asking.
A very good idea. To make this in Twitch itself.
This keeps viewers' loyalty.
Crafted cards for each tier 6 coins or 10. for new tier.
Streamheroes has done this nicely, before you have all tier 5 cards, months to years have passed. depends on how long people stream per day.
I am vote for Yess 1e comment ;)