I'm sorry Draw is not like Sketch in that way; it's not possible to import additional brushes/drawing tools. And, for a little more bad news... the only way to bring Draw content into Sketch is to bring it into an Image Layer (it could be a part of your composition, but it would not be an editable drawing).
This is real bummer, severely limited the usability of Illustrator Draw. Is this a feature the engineers are working on implementing in the future? Seems like a heck of a missed opportunity.
Sorry for taking so long to respond.
This is definitely a feature that's being considered by the drawing team. Unfortunately I don't have a timeline or more information that I can share.
I'll for sure pass your comments along to the product team.
I agree - more brushes is a must!