I would agree and also vote for a well specified data format like LAS which seems to have plenty of metadata fields in its header which would be useful for a map manager in the localization stack that would need map generation data like the timestamp and min/max values.
Though, my opinion would be to first formally identify/specify the requirements for a map file and then make sure
LAS(or any other candidate) format will cover all of the metadata needs for our use case before making any effort.
For autoware.auto, to not rush a premature decision and maintain the velocity in the development of the localization stack, we can maybe use a simple separate yaml/json metadata file for each map for now while the necessary tools for the new selected format gets implemented/ported in the parallel unless a pcd compatible solution is already available. With a decent level of abstraction on the file handling, migrating to the new file format then should not be hard.