Thanks for your question, it's not that strange at all. Here are some answers to each of those questions:
- Enemy Cards and Zones will be a major feature of the Card Game Combat v1.7.0 update which is scheduled for 2025. There are workarounds that allow enemies to use Card abilities but you can't make them draw/discard/remove Cards as they don't have those game objects. For Mahjong, you can set it up to be actions between a party of 4 Actors with a dummy enemy (that is non-interactable so the Battle scene does not end until one Actor has achieved the victory condition). Actors have individual Hands, Deck and Discard Zones which would be perfect if you want to simulate Mahjong gameplay in this manner.
- Visible Discards are not possible with Enemies as they do not have their own Hands yet but are possible with other Actors who have their own Hands. You can also enable peeking at the other Hands of Actors or turn it off as I believe that is usually not allowed in most Mahjong variants. It terms of stealing Cards/Tiles, this can be done by creating a Custom Zone that serves as a shared Discard and allowing each Actor a chance to steal a Tile and add it to their Hand when it is added to the Discard.
- Yes, you can manipulate the Opening Hands by using the Equip Cards and Turn Start Plus plugins. This would allow you to give an accessory item Notetags that add a specific Card to your opening Hand without fail each match/battle.
Hope some of this helps. What you are trying to do is possible, it will just require a lot of smart scripting to circumvent core behavior of Card Game Combat in order to achieve it. We would be happy to help point you to where in the plugin you will need to make the necessary changes to build your system :)