How will you shift Hogwarts' balance of power? It feels like all of the popular and powerful wizards
Hmm, really? Some of the absolute biggest ones (Dumbledore, Harry, Voldemort, etc.) came from there, yes, but we give too little credit to the lesser ones who haven't done too badly themselves:
You may call this lies and deceit, but I see a Ravenclaw who went on to become so proficient with the Memory Charm that he deceived nearly the entire wizarding world with his opportunistic behavior. He achieved popularity, recognition, and 'success' as well.
“Wit beyond measure is man's greatest treasure.”
Well, it must've taken some real wit for Lockhart to sniff out the right opportunities and steal others' glory. I'm not condoning this sort of deception, but we have to give him credit for having kept up this ruse for so many years.
Sort of an unrelated point, but let me point something out which so many fans have forgotten, and it's something that made me appreciate Lockhart a tad more.
‘I think I’d better teach you how to block unfriendly spells,’ said Lockhart, standing flustered in the midst of the hall.
What do you notice about that line? It was Lockhart, even though he was hilariously incompetent, who saw it fit to have the students learn how to defend themselves first. Through all his falsehood and pretense, he still at least tried to do something right as well.
Too bad the film left this out and gave it to Snape.
I know this question is about the absolute giants of the wizarding world, but I'm just listing some things in favor of the other houses.
Lockhart may have been a con artist of the highest order, but it's the fact that he got to that point which earns him some degree of recognition from myself.
Con artists are occasionally smart folks too; they just take a different route to 'success'… not that I'm saying people should join them.
Just think about it: the wizarding world is supposedly way smaller than our Muggle one, so it should have been far harder for Lockhart to have stolen so much glory from so many folks (enough to write books about those adventures) and get away with it.
Another evil representative of Ravenclaw House, yes, but think about what he achieved. Quirrell managed to keep Lord Voldemort hidden on himself from nearly all the staff of Hogwarts, including people like Minerva McGonagall, for almost a year! That's no easy feat, not when you consider all the times where he was uncomfortably close to them (mealtimes, staffroom breaks, etc.).
Heck, even Snape might not have known what was going on until Dumbledore clued him in, such as:
“Keep an eye on Quirrell, won't you?”
A Hufflepuff who was chosen fair and square by the Goblet of Fire itself, and he beat entrants such as Angelina Johnson (Gryffindor), Cassius Warrington (Slytherin), and who knows how many others to get picked as Hogwarts' Champion. In short, Cedric could have gone on to become a great wizard indeed, if not for his untimely demise.
If not for external influences, Hogwarts would have been represented by a Hufflepuff in the Triwizard Tournament.
A Ravenclaw who went on to become a champion of dueling. Then he spent years as a competent and proficient Charms professor at Hogwarts. Both of those are respectable achievements.
This isn't strictly about her Metamorphmagus ability, because that's a congenital gift.
I've listed Tonks due to the fact that she chose to make good use of both her natural talents and skills to become a fairly decent Auror (which isn't an easy task in itself). And she was gifted enough for Dumbledore to accept her into his Order; another few plus points for Hufflepuff right here.
Overall, the biggest of the bunch did come from Gryffindor and Slytherin, yes, but we can't say that the other houses didn't produce their own notable names as well.
So, in the end, I wouldn't try to force a complete change and shove better folks in Hufflepuff and Ravenclaw, no. What we got in canon was more of a plot thing ('Good' vs 'evil', hence Gryffindor vs. Slytherin), and that's kinda why we don't see as much of the Eagles and Badgers compared to the rest.