Having gone through this twice, I'd say it is not that difficult, but could take reasonably huge effort. On par with turning your crufty CMakeLists to be so cal

Having gone through this twice, I'd say it is not that difficult, but could take reasonably huge effort. On par with turning your crufty CMakeLists to be so called "Modern CMake" (whatever that means). But, why? Bazel is very opinionated on how you layout your C++ source code in the repository, and it's something which could not be retrofitted easily.