I agree that the advantage of having both the odom frame and the map frame (conforming to REP 105) enables the opportunity to combine different use cases at the same time: For example road user tracking (odom) and global localization (map). A.f.a.i.k., the unintuitive TF tree, with a map-to-odom publisher, is enforced since TF consists of a tree structure: Any frame can only have a single parent. Multiple childs are allowed. However, having the map and odom frame as childs of base link seems unintuitive as well. I don’t know if there is any plan to change TF into e.g. a graph structure at some point.
If the autoware localization would comform to REP 105, that would also make it easier to combine autoware global localization with the robot localization package (or the newer fuse package[2]) for (smoother) odometry estimation.
[1] https://github.com/cra-ros-pkg/robot_localization
[2] https://github.com/locusrobotics/fuse