Since lactation/breast feeding is already featured, is breast expansion/growth also included or planned?
We contemplated it but it is not currently planned for the main story. However, once we hit V1.0 (~3 more updates) we will go into the "Epilogue" phase in which supporters (Patreon/SubscribeStar) will have the opportunity to vote for isolated stories/scenes (can be earlier, in the middle, or after the main story) with positions and kinks they would like to see.
TLDR: While it's not currently planned, it's possible that it will make an appearance in the game.