This seems to be assuming the utility abilities won't scale, and that's a worrying assumption. Being able to disassemble dungeon traps and then reemploy them would definitely scale, and I see no reason the variety of perception abilities available to SED wouldn't scale either.
Yeah, but that will also be true to an extent of an outsourced "Utility Mercenary" you hire; given that Skill Levels scale on practice using rather than XP. Although adding in items probably changes this somewhat, they can collect a fee for their services and purchase items. Overall, you might expect a "utility mercenary" to end up somewhat worse in their niche than a character participating fully in killing bosses with the same class, and much worse in combat obviously... but that might still be a positive-sum trade if it allows the character with strong scaling abilities to level/gear up much harder.
Bluntly, whilst I think there are certainly likely to be scaling benefits from a lot of utility abilities, they are not necessarily intended to be equal. This is a dungeon crawling game, and at the most fundamental level, our progression depends on the ability to kill lots of bosses. The format kind of requires that not all abilities are equally useful in all contexts, or optimisation has no point, and we know already that optimisation is one major aspect of the game.
Now, there are certainly likely to be "utility" classes which start rather weak, and by level fifteen are going "Haha, fuck you, I'm behind a hundred mimic chests I've charmed to serve me". But in the very rough schema where I'm splitting "utility" out from "combat/magic
/shenanigans", that would probably fall somewhere under "shenanigans". What I'm talking about are classes which genuinely focus more on utility at the expense of scaling power - and we know these exist, because we've seen a lot of classes, and Levi has explicitly told us that all classes are not all made equal.
Taking SED as an example (which is a class I like, and would be my second choice after BOF, don't get me wrong), we know roughly what its abilities are and how they scale, because it tells us in the description. Unless there are some form of "prestige classes", it seems unlikely to me that Danger Sense and Acute ears will beat out Punishing Strike/Murderous Attack/Regeneration in pure combat utility, or that Spot will beat out Plus One in terms of extra resources gained over the course of a floor. Now, these skills are much more useful
out of combat, especially Pathfinder... hence why someone with those abilities might rent them out to a party who can thereby focus more on combat or accumulating exponentials.
Now, this is all taking it from the perspective of what is most mechanically "optimal" - which is not necessarily the most important way to enjoy the Quest! (It's not why I chose to vote for BOF.) But if we're thinking essentially in terms of economic logic, looking for potentially positive-sum trades becomes more relevant, I think.
Also, it means there is potentially a way for the Astronomy Club to survive by camping out in safer areas and hiring out members with utilities to other parties (if they have enough utility classes in their group), so I'm interested in the concept for that reason alone.