I instantly fell in love with Bike, because of its elegance, performance, and minimalism. Thanks a lot for creating such a fantastic product!
I can imagine a lot of additions (but a value of keeping Bike simple), but these three are the most obvious for me:
The ability to search for tasks (maybe by their  shortcode?)
The ability to hide all non-matching nodes when searching for something. I first saw it in Workflowy and immediately loved its elegance for large outlines. It should allow me to expand sub-nodes on a node that matches the search term.
A way to directly reference nodes by pressing @ and starting to type the content of a node