Would it be possible to implement a changable set of rules while hosting a friendly game? something like "cheat" option in AI games, which would extend the possibility to play hidden/non-hidden cards and short/long mode.
settings that could include changes in starting values (tower, wall, facilities, stock) and victory condition values (max tower, turn limit, max resources,...), only one type of victory (ignoring other "victory conditions"): e.g. tower building victory where your tower can drop to 0 while not trigering "destruction" victory; or possibility to play with only some cards (common/uncommon/rare, or cards set via filters)
it is just an idea, I dont know whether it would require any significant intervention into code...