Overview

I am making* a robust wheeled-quadruped robot that can operate in "human-scale" environments. It's a massive undertaking for me that's both a creative outlet and an excuse for me to learn new things. Heavily influenced by sci-fi and R2D2 builders around the world but I'd like it to have some practical applications too.

Crude concept - work in progress

Because I keep moving the goal posts it's tricky to categorise; it's not a "droid" in the traditional Star Wars universe sense, but then "robot" didn't seem quite right either. It became Droidbot, inspired by robots real and sci-fi.
*Always seem short on either time, money or energy to get anything done in reasonable time frame.
Also see Status on TL;DR.

Ref: Origin, Goals, aspirations & risks 

Original Motivation

• Wanting to build a larger "human-scale" robot with plenty of room for development. 
• Make something with some cool sci-fi widgets (for fun), a "droid" shouldn't be too difficult. Wheels are easier than legs. Both would be ideal. No bipeds. Revisit old model-making skills to add character. 
• Get hands-on experience of control systems, sensors, communications etc. Improve and expand hardware and software skills. 
• 3D printing would make some mechanical parts more accessible and make design iteration easier. Improve 3D modeling skills. 
• A reason to learn/implement ROS (I know, I could do so with a small rover, but that wouldn't hold my interest).

Evolution (part 1)

• A traditional droid's design (& IP) limits development options. Moving further away from the droid idea. 
• Needs to be capable of operating on reasonably rough terrain, rain, mud etc. I like the great outdoors. Rated to IP54 at least.
• What's the point (other than self-improvement)? Practical uses for such a thing?

Evolution (part 2)

• Sci-fi elements became less important. 
• Make it as robust as reasonably possible. No one likes fragility. 
• Better to steer efforts in direction that could be useful elsewhere.
• Added remote control & tele-presence to the requirements/goals.

Goals

Here's a list of what I hope to achieve (both short- and long-term).

• Large enough to operate outdoors and in limited human environments. Think R2-D2 size rather than table-top or carpet rover. Costs will be higher though. 
• (A little) Sci-fi styling here and there. 70's and 80's childhood of Star Wars and Alien(s) having a big influence.
• Four stowable wheeled-legs allowing staged development with modes of travel:

1. Compact 4-wheel slow manoeuvres.
2. Expanded (stable) 4-wheel manoeuvres.
3. Quadrupedal walk.
4. Compact 2-wheel balance.
5. Expanded 2-wheel balance.
6. Upright 2-wheel balance (think Boston Dynamics' Handle).
7. Bipedal walk?

• Head tracking and remote viewing for tele-presence.
• Two main arms for remote manipulation. Possibly a smaller arm (or two) for more delicate tasks.
• Learn Linux & ROS. On-board Raspberry Pi(s), Arduino ROSnodes and monitoring/control via laptop and/or custom remote.
• Investigate higher level behaviour algorithms, machine vision, mapping, speech recognition, speech synthesis and AI.
• Investigate possible practical applications. I'm thinking disaster relief with appropriate sensors and equipment. Skill transmission via tele-presence. Provision of power? Water filtration? Load carrying? Security monitoring and warning?