e.g. Can I combine the Google Calendar, Mail, and Asana packs into my own custom pack?
You would need to rewrite the code.
Connected with you on twitter! But for those here the answer is no
Packs, for security purposes, can only hit a single domain.
Therefore, you could rewrite and make a pack that hits several google APIs in one, or several Microsoft services in a single pack, but you could not create a pack that hits multiple services/domains.
But you CAN make multiple packs and then combine their actions into advanced inter-related workflows inside of a single document
If I remember correctly you can ask Coda to allow your pack to address multiple domains. If this is a private pack, I can’t think of many reasons to not allow you to do so.
But, I don’t think there are that many advantages to putting these functionalities in one pack and like Piet says, you would have to develop (and maintain) your own pack.