Well, so much for my Haxorus example of being a Risky Pokemon to use. Moving on though to answer the questions bugmaniacbob has placed:
1. What should the build of our Pokemon be? (eg. Bulky offensive, hyper defensive, etc)
I believe we should focus our pokemon to be leaning more offensively. Of course, it could have a defensive set as well (much like Salamence/Dragonite can be a threatening Set-up sweeper, Choice abuser, or defensive threat), but on the whole offensive is far more Risky than defensive simply by its nature. Dual Screens + Healing Wish may be interesting, but in all honesty, if a Pokemon had to take a risk to set those up it wouldn't be effective. Players use screens and other such strategies on Pokemon to have a reliable way to set up, not struggle.
2. What facet of strategy should this Pokemon's focus be on? (eg. Support, hyper offence, etc)
I dont think Risk should be limited to any one type of strategy or type of team. This Pokemon should be able to function well on nearly all variations of playstyle: namely Balanced, Bulky, and Hyper. Pure stall and Semi-Stall are too focused on risk minimalization, which is why I excluded it from the list. By focusing on only one playstyle for this Pokemon, it could severly limit its viability in OU.
3. In which parts of the process should we focus on Reward, and in which should we focus on Risk? (eg. Low Speed so reliance on set-up moves, etc)
Typing and a reliance on set-up moves/choice items would be my first targets to introduce risk into this Pokemon. Typing is obvious: In an extreme case, if you were to have a Pokemon weak to Ground, Ice, Water, Fighting, and Rock the risks of using it would be huge. Meanwhile, a reliance on set-up moves makes it taunt/phazing/excessive switching vunerable, while Choice reliance makes it easier to wall. If we focused on those aspects, while giving it the stats, movepool, and specific enough resistances to still be viable, I believe it would be an effective high risk/ high reward Pokemon.