The combine two bots just fork one, and export the others responses into a response list file from the "Training & Chat Logs" page. Also export any scripts that differ. Then import them into the new bot.
You can also forward chat request to another bot, such as this example Self script that uses the Bot Libre web API,
Or the SRAIX calls from the AIML2 example,
Using SRAIX you can even call other AIML2 compatible bots on other servers, or even any bot that has a web API.