I think about something similar to Corel LiveSketch in Affinity Designer:
https://www.youtube.com/watch?v=gYdxHxdl7EI
I can find video but in Illustator was similar function (probably CS6, other version - I don't know). When you drawing line you can adjust his shape by drawing part of them again.
In short: fx. you're drawing curvy line. Next you are adjusting this by drawing them few times on tablet. If you're drawing some part not stright line but more similar to circle line is changing in real time to more curved. It could be alternative to pentool and make sketching for some people easier. For me more natural is use few shorts lines to make one longer. (Of course this functionality don't replace talent, but this idea looks interesting as extension of Bezier curves etc.).