Is it possible to load a `sys.config` file from `config.exs` somehow?

For historical reasons we receive a classic sys.config file to our project, that contains all the configuration settings. While it isn’t particularly hard to convert it into a config.exs, I would like to know if there’s another way to include this file into a Mix/Elixir project.

Is it possible to somehow include a sys.config file into an ordinary config.exs conf file?

I made a Config.Provider that can load a sys.config file into the system, but as far as I understand things, this only helps with releases, not the normal development methods (iex -S mix). Is this true?