Have a way to make a set of collections (not every collections playlist) subscription locked. There is a way to make a whole channel subscriber only viewing. Why not have it to where a broadcaster can lock a set of videos for those who chose to support the streamer financially while not taking away from those who can't or choose not to subscribe? In this concept, being able to keep past broadcasts and other uploaded content not in that collection completely open to everyone.
Idea behind it: I like to edit streams and other content into condensed highlights and upload them to Twitch and YouTube, my concept in doing this, is to remove the third step of redirecting subs to another place such as Patreon or Discord for access to videos early. Having a place on Twitch would be much easier to allow subscribers early previewing/first looks on content before it becomes public to everyone. This way it would give another perk to subscribing if this is something the broadcaster does, without forcing the viewer to be apart of another process.
But it's not just limited to the idea of early content viewing, this would also add another option of having permanent subscriber only content in the same way there is sub only streaming.

Provide custom servers for channel subscribers/twitch prime - this would allow streamers to play with their communities without the hassle of renting a server, plus you could charge more for prime if it was included to be able to join a custom server of the person you use your prime sub with. It would stop stream snipers as the streamer would have total control over the server, plus as it would be provided by Amazon, they would be able to use all the latest security to avoid it being DDOSS'd and hacked.

I feel this is really needed for certain games that are prone to being DDOSS'd on custom servers like Battlefield 4, and most likely a lot of other games.

Changing the way the founder badge works would be nice. The current system allows 10 founder badges for Affiliates and the Partners, 25.

My proposal is to allow people who sub in the first 24 to 72 hours of the streamer getting the sub badge to get a founder badge, if the streamer does not get up to at least 10 founders in that time frame, it will continue until the 10th founders badge is there. That way, for people with bigger communities, they people who sub day 1 still get rewarded, since they are still technically founders, just unlucky to be sub 26 by a few seconds.

It's just annoying when a community of people all sub day one, and majority get cut out due to small limitations. Also, most founders in many channels are no longer there, so it makes it even more scarce after years of streaming.

Even allowing the streaming an option/rules to the founders badge themselves as partners could be a good incentive.

What i honestly could only come to in addressing possible issues involving the subsctription system is perhaps the overwhelming or unrealistic feeling one may have when indeed the community they have sewn together truly works to financially support them by buying a subscription, typically voluntarily, for to see a streamers work. I suspect that perhaps giving 1 free sub for making affiliate or partner, 1 gift sub for the chat to use in the very next stream, and have both be given and financially valid from twitch, as it would make a person say to themselves "Alright, its not too much money lets not get carried away or begin manipulating your audience. The ability to also have a gifted sub be given in their next stream may help the audience in the chat realize the streamers new norm and can facilitate the surge of the true subs a audience begins to invest starting from the first day of financial responsibility of the streamer qualified.

If you want to gift multiple subs, you can let Twitch pick randomly, giving those subs to trolls, bots, and others. OR you can click each persons name, and gift directly, multiple times. And if you gift multiple times, it can be seen as spamming - and yes, some streamers get mad about being given money like this...

Now, there are multiple feature requests for a better algorithm for selecting users to be gifted a sub. None of which have been acted on in over a year. Perhaps it's tricky to determine the fairness of such a change.

However, generating a simple check box list of unsubscribed users, that a gifter can select from would avoid the downsides of the current auto-selection, would be utilized by those specific users most interested (as to not negatively impact anyone who dislikes the change), and would be simple to implement.

For clarity, this would exist alongside the current "choose for me" approach. A gifter would be able to either method.