How to invoke bash, run commands inside the new shell, and then give control back to user?

bash --rcfile <(echo '. ~/.bashrc; some_command')

dispenses the creation of temporary files. Question on other sites:

• https://serverfault.com/questions/368054/run-an-interactive-bash-subshell-with-initial-commands-without-returning-to-the
• https://unix.stackexchange.com/questions/123103/how-to-keep-bash-running-after-command-execution