Ssh with dynamic ssh config :-P Modify it to suite your needs

ssh.bash

#!/bin/bash
# g@ut.am

SSHCONFIG_Linux=$(cat << 'HERE-DOC'

Host *
  StrictHostKeyChecking no
  ServerAliveInterval 60
  ForwardAgent yes
  ServerAliveCountMax 4
  ServerAliveInterval 30
  SendEnv LANG LC_*
  Ciphers arcfour,blowfish-cbc
  ControlMaster auto
  ControlPath   /home/gautsing/.ssh/tmp/%h_%p_%r
  ControlPersist 48h

HERE-DOC
)


SSHCONFIG_SunOS=$(cat << 'HERE-DOC'

Host *
  StrictHostKeyChecking no
  ServerAliveInterval 60
  ForwardAgent yes
  ServerAliveCountMax 4
  ServerAliveInterval 30
  SendEnv LANG LC_*
  Ciphers arcfour,blowfish-cbc

HERE-DOC
)


SSHCONFIG_Darwin=$(cat << 'HERE-DOC'

Host *
  StrictHostKeyChecking no
  GSSAPIAuthentication no
  ServerAliveInterval 60
  ForwardAgent yes
  ServerAliveCountMax 4
  ServerAliveInterval 30
  SendEnv LANG LC_*
  Ciphers arcfour,blowfish-cbc
  ControlMaster auto
  ControlPath   /Users/gautsing/.ssh/tmp/%h_%p_%r

Host bitbucket.org
  HostName bitbucket.org
  PreferredAuthentications publickey
  IdentityFile ~/.ssh/metagog@bitbucket.id


HERE-DOC
)


# Program's name
PRG="$0"

# Check if we are symlink
while [ -h "$PRG" ]; do
  ls=`ls -ld "$PRG"`
  link=`expr "$ls" : '.*-> \(.*\)$'`
  if expr "$link" : '/.*' > /dev/null; then
    PRG="$link"
  else
    PRG=`dirname "$PRG"`/"$link"
  fi
done

# Directory containing program
PRGDIR=`dirname "$PRG"`

# Function emulating which
# takes additional "path" argument
# and exclude it when searching $PATH
function otherwhich () {
    local f; f=$1;
    local d; d=$2;
    local c; c=0;

    for path in ${PATH//:/ }; do
        if [[ $path != $d ]]; then
            [[ -x $path/$f ]] && c=$[ c + 1 ] && echo $path/$f && return;
        fi
    done
    [[ $c == 0 ]] && echo "which: no $f in ($PATH)"
}


# Wrapper are ssh
# which does the real work
sshwrapper() {
    # pass path to real ssh to execute
    local ssh; ssh=$1
    shift

    # Is ssh executable?
    [[ -x $ssh ]] || exit 1

    # we will create fifo in TMPDIR
    TMPDIR=~/.ssh/tmp
    mkdir -p $TMPDIR 2>/dev/null >/dev/null
    [[ -d $TMPDIR ]] || exit 1

    UNAME=$(uname -s)
    case "$UNAME" in
        Linux)
            tmp_fifo=$(mktemp -t .ssh.fifo.XXXXXXXXX)
            ;;
        Darwin)
            tmp_fifo=$(mktemp -t .ssh.fifo)
            ;;
        SunOS)
            tmp_fifo=$(mktemp -t .ssh.fifo.XXXXXXXXX)
            ;;
        *)
            echo 'unsupported OS'
            exit 1
            ;;
    esac

    # bailout if tmp file not there
    [ ! -e $tmp_fifo ] && exit 1

    # delete the tmp file, create fifo immediately
    # cat/echo the ssh config to fifo
    rm $tmp_fifo && mkfifo "$tmp_fifo" && (
        if [[ -n $(eval "echo \$SSHCONFIG_$UNAME") ]]; then
            echo $(eval "echo \$SSHCONFIG_$UNAME") > "$tmp_fifo" 2>/dev/null &
        else  
            config=$HOME/.ssh/config
            [[ -f "$HOME/.ssh/config.$UNAME" ]] && config="$HOME/.ssh/config.$UNAME"
            cat $config > "$tmp_fifo" 2>/dev/null &
        fi
    )

    # execute ssh and pass fifo as the config file
    $ssh -F "$tmp_fifo" "$@"

    # rm the fifo file
    rm "$tmp_fifo"
}


# Find the real ssh exec
SSHPATH=$(otherwhich ssh $PRGDIR)

# run function pass ssh path, and args if any
sshwrapper $SSHPATH $*