So happy to see Wizards finally making an effort here to create something polished.  As a DM & software developer, I've wanted to do something in this space but have found it challenging to do (well) these three things: 1. create the architecture to handle game mechanics,  2. manage the content for the game, and 3. build an interactive UI for the different perspectives of the game.

I'm confident Wizards is in a better position than me to handle the first two.  So here's some thoughts on the UIs:

World view

• A map view to show your character's location in a setting, e.g. Sword Coast
• The ability to communicate with other players in the setting
  • City/Town posts (forum)
  • Inns (chat)
  • Party (video/voice)
• The ability to create a party from a group of players
  • Party has a leader
  • Party can have saved formations
  • Party has group treasure and accounting tools
  • Party view is available

Party story view

• Map/art based view for role-playing and logistics
• Movement scale/speed is overland (city to region)
• DM & Party can write in party journal (adventure log)
• Explored overland and dungeons are "auto-mapped"
• DM can place party into interactive view

Party interactive view

• Centered on party leader
• Movement scale/speed is local (room to building)
• Party has a birds-eye view of immediate map
  • Tabletop map with graphical minis
  • Light sources and character vision handled

• Leader performs coordinated moves until combat or another event
• Combat makes interactions turn based
  • Initiative management
  • Spell effect management
  • Characters can perform their qualified actions on their turn
  • Graphical spell effects (spontaneous and lingering)
  • Combat sound effects

Character view

• Character sheet
  • Story view: highlight skills, conditions
  • Combat view: highlight attacks, equipment, hps, saves, spell effects
• Spells
  • Manage known spells
  • Favorite spell list
• Store
  • Equipment sales/purchases