Like rejuvenating a sun by 8 billion years and still being at 100% charge by replenishing through ambient hope.
Yeah, Saint Walker pulled that off. Precisely one time. On a planet that was dying, and whose mythology was so in line with him as their savior I suspect time travel or precognition must have been involved. Also, he presumably needed to use radio transmissions to make everyone know they had to lend him their energy for the Spirit Bomb, because he sure as shit wasn't making any constructs to do it.
Alternatively, he burned up his ring's charge fixing the sun, and then desperately raced back to his homeworld to soak up the hope its inhabitants emitted as they realized their sun was getting brighter before he ran out of charge completely and his environmental shields winked out.
Like recharging green lantern rings even over 100%, in prime continuity they were given the ability to recharge any color ring.
That's not really a benefit for any Blue Lantern who doesn't want to be dependent on some other, luckier soul to actually do things. "You're super good at being another ring-slingers' subordinate" isn't exactly a wondrous gift of the cosmos for the Blue Lantern.
Like healing far better than other rings.
Sort of like how the Indigo Tribe can teleport across the galaxy, which is why they don't have constructs either. Oh wait, they do, and are pretty good at healing bodies & minds to boot,
and they can mimic other Lights' gimmicks. Once again, either Hope is for losers or these rings are whack.
Or trumping red rings by calming their rage, trumping yellow rings by draining their charge, and trumping orange by blocking their energy absorption abilities.
That could just as easily be a special technique, a la how Larfleeze assimilates anyone he kills, rather than a basic power of the Blue Light.
Anyone who thinks adding 8 billions years to sun's lifespan is weaker than punching someone with a construct just isn't blue lantern material, I suspect.
In terms of combat utility? I would indeed assume that being able to rejuvenate a sun is less useful than being able to manifest a zeta flayer construct. And the thing is, what "Blue Lantern material" even
is is still very much a point of contention, considering my entire argument rests on the idea that Ganthet deliberately crippled the rings and then programmed them to seek out people whose
hope manifested in an entirely pacifistic, humanitarian form, because he didn't want warriors in his Corp.
Hope can carry a sword just as well as
Rage or
Will or
Avarice. Denying the Blue Lanterns a means of offense seems more a choice of the Corp's founder than a matter of metaphysics.
And if one gives them all the abilities of a green lantern in addition to that, the comments would be along the lines of "There are two types of lanterns, blue lanterns, and losers who wish they were blue lanterns."
Yep, that's what you get from A) bobblehead malware, and B) a ring designed around minimizing the mental influence on its users and ensuring its power remains in the hand of its makers rather than its users, not necessarily in that order. The fact that the light of
"don't you fucking tell me what to do" is being used to successfully power a military organization built around
obedience to a hierarchy makes me suspect the Light's natural tendencies are deliberately placed second to... other concerns in the rings' search protocols.
From a Doylist perspective, it's mostly an issue of Green Lantern rings being the first ones we had, so they kind of missed out on the special powers lottery when they started coming up with the Emotional Spectrum. The fact that they're a monolithic, well-established organization supported by living gods when most of the other Corps are fringe groups with little backing might also tip things a little.