Drawing directly on the notes is not something we have considered yet, although it's supported when importing notes with drawings from OneNote. The obvious challenge is that notes with drawings lack flexibility - the text can't be reflown in particular because the drawings will no longer be aligned with the text. However Joplin notes may appear in many different contexts (mobile, desktop, web). I guess we could have a special "frozen" layout when some drawings are made on top of a note.
Note that you can also use the recently added drawing feature to make various drawings, add text, etc. but this is done within a canvas, not on top of the text.
As for handwritten recognition, this is in progress: Project 4: Handwritten Text Recognition (HTR) for Joplin | Joplin