Use /bin/bash when using Bash specific shell commands

I have a bit of an issue when trying to use capistrano/sshkit. Our user account is setup to use tsch for legacy reasons. I can try to talk to them about changing to bash, but would have better luck (and could probably help others), if we can just run bash specific commands using /bin/bash or we are able to set the bash shell using some kind of variable (`set :bash_shell, '/usr/local/bin/bash'`)?

PS wasn't sure to put this on here or Capistrano, but I think here would make a bit more sense.