StartupItems/ServletContainer

適当にでっちあげました。
/System/Library/StartupItems/ServletContainer/ServletContainer

#!/bin/sh

##
# Servlet Container
##

export JAVA_HOME=/Library/Java/Home

. /etc/rc.common

StartService ()
{
    if [ "${SERVLET:=-NO-}" = "-TOMCAT-" ]; then
        ConsoleMessage "Starting Tomcat Servlet Container"
        /usr/local/tomcat/bin/startup.sh
    elif [ "${SERVLET:=-NO-}" = "-RESIN-" ]; then
        ConsoleMessage "Starting Resin Servlet Container"
        /usr/local/resin/bin/httpd.sh start -J-server -Xms32M -Xmx64M
    fi
}

StopService ()
{
    if [ "${SERVLET:=-NO-}" = "-TOMCAT-" ]; then
        ConsoleMessage "Stopping Tomcat Servlet Container"
        /usr/local/tomcat/bin/shutdown.sh
    elif [ "${SERVLET:=-NO-}" = "-RESIN-" ]; then
        ConsoleMessage "Stopping Resin Servlet Container"
        /usr/local/resin/bin/httpd.sh stop      
    fi
}

RestartService ()
{
    if [ "${SERVLET:=-NO-}" = "-TOMCAT-" ]; then
        ConsoleMessage "Restarting Tomcat Servlet Container"
        /usr/local/tomcat/bin/shutdown.sh
        /usr/local/tomcat/bin/startup.sh
    elif [ "${SERVLET:=-NO-}" = "-RESIN-" ]; then
        ConsoleMessage "Restarting Resin Servlet Container"
        /usr/local/resin/bin/httpd.sh stop
        /usr/local/resin/bin/httpd.sh start -J-server -Xms32M -Xmx64M
    else
        StopService
    fi
}

RunService "$1"

/etc/hostconfig
に

SERVLET=-RESIN-

という行を作る。
RESINかTOMCATを選ぶ。