I frequent several lower traffic sites. (RPG, Christianity, gardening, and Sports to be exact) and while we do not have the kind of traffic that SO does, and we do not have anyone with either of the badges you mention at this time, they are achievable on these smaller sites. Let me tell you why I think so:
They are counting stats badges meaning that eventually everyone can get them on any site. Yeah some times it's really hard to cap out on a site (I've capped out exactly once on RPG, and I have <12k rep there). But it does happen, we have users are on RPG who have capped 10-15 times. That's part way to Epic and will eventually get to Legendary it just may take a few years (and that's a good thing, legends aren't built quickly).
These flags have plenty of flag opportunities. We get several flags a day on Christianity, and there is plenty of other content there worth of a flag if people were looking for it. Again it's not like there isn't content worthy of flags on every site. Even on sports where we have a topic much less contentious than Christianity, I've found enough posts worthy of flags to rack up over 50.
Gold badges should be hard. Even the easy gold badges are pretty hard (Fanatic and Electorate are the easiest, and fanatic takes 100 days, and electorate takes at least 15). But populist is just as rare on beta sites as is reversal.
If any badge deserves looking at it's unsung hero. That's one that is tailor made for the kind of traffic SO gets, but falls apart when every question gets views and votes like on many beta sites.
Anyways. I don't see any reason to change the badge thresholds because I think getting a gold badge should be special.