Reasonably scale mid-roll time/number required to disable pre-roll ads to the size of the channel.
The size of a channel matters when you are looking to make ad revenue. Larger audiences are likely to have a larger number of potential ad viewers. Obviously, the sub/non-sub viewer ratio is important, but larger channels are likely to have a higher potential for ad revenue than smaller channels.
Scaling the time needed to disable pre-roll ads will encourage smaller channels to run ads. When pre-roll ads are disabled, there is a higher chance a new viewer will enter the channel potentially helping to grow that channel.
To "tag" along with the idea, add a tag under a preview window showing which channels have pre-roll ads disabled so the viewer doesn't waste time waiting through a pre-roll ad to see if they may like the channel's content.
Ads should be created to work with the live stream, and not force the live stream to work around ads. Shaping content around ad breaks feels scripted and takes away from the "live" experience. In most cases, there are not enough viewers in a smaller channel to encourage the streamer to run ads to increase their monthly income. So, in turn that channel does not help support the platform. Working to scale ad run times with the size of the channel has the potential to help both the streamer and the platform.