Please add standard CMSIS-Core headers and register definitions. Ideally these would replace the bespoke headers to avoid fracturing of the ecosystem.

The common CMSIS header files are here. It's not uncommon to include the entire CMSIS_5 repo as a submodule, and it's just as common to copy the headers into your SDK.

CMSIS-Core documentation

CMSIS-standard register definitions can be generated with the SVDConv utility.