I support twitch/youtube chat integration in the osu client.
As for streaming the game through the client? I'm against it 100%.
I'm a streamer who plays Osu quite frequently. Xsplit is a paid streaming service but OBS is completely free. Streaming through the client would not only make the client size larger, but would also make your playing experience bad if you don't have the hardware and internet to back it up. As Osu is a free game, I imagine the majority of people who play it don't have a lot of money to throw around to play games. Perhaps a lot of you may play league of legends, which is also a free to play game. I'm not implying Osu is an inferior good, but merely showcasing that the majority of players don't have the hardware to support their computer doing a lot of things at once.
Having the required bitrate is also a factor. If you're living in 2018 with DSL internet, clearly you don't have the capacity to stream a game. If you're playing on a laptop with a weak or old CPU, not only are you literally destroying your hardware at a faster rate by trying to stream it due to the increased heat but you will also experience lag in the game AND in your stream. It's not some magical process.
On the streaming side of things, yes, I have watched some Osu streams. I've watched people with a couple hundred viewers, and also no viewers. Not all, but the majority of low view count streams include issues where there's no face/hand cam, (im shy xdd uwu) no microphone, a really quiet voice, or extremely limited interaction with the chat. Now, how are all of these things going to be implemented into the client? They're not.
I can tell you this: you might enjoy streaming for what it is, but no one is going to care about what you have to show on your stream unless you have something to offer. Would you watch an attractive naked streamer? Most people would. Would you watch a funny streamer? Most people would. Would you watch a near-pro level streamer? Most people would. What does your stream have to offer? None of these things. No one is going to care about your stream if you're naked but your camera is off, your mic is muted because the key presses are too loud or you're shy, and 99% of people don't care that your score got you ranked 11,000th out of 26,000 other people. Twitch is about interacting with your audience and I believe that just isn't possible with an in-client stream.
By having low quality streams with the factors listed above, not only does that make the game look bad, but a casual twitch viewer (who may not even play) won't want to watch a stream from a game that looks like it's barely functional. This will lead to the general consensus that the game is bad, poorly optimized and for an incredibly small niche of people.
TL;DR Your laptop is trash, don't even bother streaming the game. If you try, you will make all the other streams look bad.