Only if he understood grappling and ground fighting and had actually trained for years full force against someone of Royce's ability.
Yes, he'd have to do significant practice on the ground. Without doing that, he'd be quadruple amputee swimming in a pool with a shark.
As far as practicing a different style, I suppose, eventually he'd figure out what to do on the ground, but it sure wouldn't look much like wing chun. It would be a whole lot more efficient simple to learn a style that specializes in ground fighting.
If you do not train to fight against something then you will NOT have any experience on how to deal with it.
Now, if the skill level difference is VERY high, that may not matter BUT if there is any decent amount of skill on the part of the opponent and he brings something to the "table" that you don't have any experience with, the advantage is, typically, His.
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !
Well, if it doesn't work under the controlled conditions of competition, that chances if it working in the Uncontrolled conditions are, logically, less.
Competition make sit a level playing field for BOTH parties and in "the street" BOTH are free to do whatever they want.
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !
IN short:
If you can't beat someone when THEY are limited by the rules and environment, what makes you think you can beat them when they are NOT limited by them?
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !