This has nothing to do with your question, but if sainthood means surety that one is in heaven, was the typical saint vetting process shelved for the good guy crucified next to Jesus? I mean, saying that he'd be in Heaven with Him had to carry some serious weight, no?
The "Saint vetting process" that we have now began in the Middle Ages. Before that, Saints were popularly acclaimed.
St. Dismas - the Good Thief - most certainly is in Heaven with Jesus, as He had promised. If I recall correctly, he was celebrated in the Martyrology yesterday, March 25.