Not possible to run shell as if it were a login shell

I'd like to pass custom options to my shell, but I can't since no configuration option is available in ```dconf``` for it. Could a ```shell-options``` option be added? It looks as though ```run_shell``` would need amending:

https://github.com/p-e-w/finalterm/blob/master/src/Terminal.vala#L222-L232