Hey there Arya!
While I wouldn’t oppose a 5th tier, that would mean you’d have to decide how to grandfather in existing Pre-Master cutters. Would they be Journeymen (Journeypeople hehe) or Expert? I guess much of that would factor in where the Competition Committee sees that new tier being inserted (i.e., is it more or less difficult than the current Pre-Master tier?).
The other issue would simply be logistics: If USFG is having trouble getting volunteers to be stone graders, than a new tier might (or might not) be an additional load on the graders and facilitators.
If there’s no new tier, I think I tend towards Journeyman (gender specificity aside) because Expert just seems closer to Master than Journeyman, if that makes any sense. I thought that even before seeing your 5-tier proposal, which has the same idea built in.