XF 2.1 Randomization - 2 possible options ?

[Wyvh]

Greetings,
I'd like to do either of the following :

1- User 1 choses Option 1 under the post function, making User-bot 2 automatically post right after with Element 1, 2 or 3. If User 1 choses Option 2 under the post function, it would make User-bot 2 automatically post right after with Element 4, 5 or 6.
2- A custom BBCode that would allow User 1 to chose between different sets, making User-bot 2 automatically post right after with the according stuff (Element 1, 2 or 3 if Set 1 chosen; Element 4, 5 or 6 if Set 2 chosen)

Any idea how this could be done ?
Thanks.