I think I'd call auctions and banking "advanced economy" and slate that at 1.1+ as a basic MUD needn't have these things but moreso because they can be kinda mud-specific.

Instances is also an idea that crossed my mind, but I was hesitant to address it. (Edit: Link). If we want to move forward with it, I'd push for 1.1 and beyond.

Custom prompts fits with the 'settings' theme of 0.5.  This is pretty minor/easy and needn't be called out in the roadmap.  Not sure what you mean with colors; users can already cause color changes stuff with their communications and such.  (I don't think we sanitize user data yet though, to prevent malicious usage.)

Aliases/macros would fit for 0.5. (Fortunately it should be a simple matter of ripping the command out of the project if the MUD admin is opposed to them rules-wise, etc.)  Also pretty minor.

Cool ideas for in-game legal systems you posted.  I think the deep implementation details come quickly into world/game-specific territory (beyond the MUD engine) although this may allude to some MobileBehavior building blocks and the like which should be present in the core engine and proven by example.  Having a flexible and deep ArrestsBehavior which would be configurable to support customizable rules / triggers / reactions and so on as described could be suited to the 1.1+ timeframe.  Some sub-behaviors for combination with, and underlying eventing needed to enable such deep behaviors, and so on, should probably come in earlier than that.