Right now theres not enough control over how a streamer runs an their stream with the new mid-rolling. However, a feature that can be added is to disable for 20 - 30 minutes mid-rolls for the stream per 30 second ad break and mid and pre-roll per 60 second. That way, a streamer can plan their ad breaks and work around them, especially for competitive games like overwatch, LOL, CSGO, etc. Even for non-competitive games, allowing a streamer the ability to control the flow of the stream by implementing an ad break to avoid mid rolls allows them to build better relationships with viewers.

I understand that this would interfere with the dynamism of an algorithm controlled mid-rolling that would mid-roll different viewers at different times, but if the base product is deeply affected the revenue source will also be deeply affected. And the base product of twitch is the relationship between streamers and viewers.