There have been lots of players who looked special , dominated FC, and were tipped to be great batsmen and actually ended up being great batsmen. If you say there was a chance Barry Richards would've been a Mark Waugh, I say there was at worst just as big a chance he'd have been a Tendulkar/Lara type genius who actually fulfilled his potential.
It remains a "what if", but the stuff he did in WSC which had high quality attacks, and more importantly, was competitive cricket comparable in quality and intensity (for the most part) to test cricket, leads me to believe he'd have coped just fine.
However, I don't see how Pollock's lack of cricket compared to guys like Kallis automatically makes him worse. 23 test doesn't sound like much, and was no where close to a full career even back then, but it's surely a significant enough amount of tests to gauge how great he was. It's not like he played one series like Barry. He toured Australia and England with great success, ripped apart both those teams when he played them at home, in a career which spanned 7 years. His case really doesn't come under "what could have been" at all imo. It was an already great career before it was cut short by circumstances.