Do you want broken weapons/ abilities in the game?

Personally, broken weapons are useful in particular situations, so I'm for it. If I'm trying to farm for an rare item, having a broken weapon speeds up the process a little bit. I wouldn't use it on a boss or general game play. For example, in SOTN, I only used the Alucard shield or Crissaegrim on the Final Guard when trying to get the Gods Garb. Using any of this during normal game play ruins the fun, so I would only use those in very particular situations as I had previously given the example for.

Yea I definitely want them in the game.

That said, I like broken items where its brokenness is not immediately evident. The shield rod, for example, took me a while to experiment with and figure out. Same with the duplicator. Even though I had a certain sense that it had potential and it certainly was pricey, it didn't really click until I picked up a Power of Sire, which by itself is not broken either. So yeah, certain items being broken but only when used in the right combination with other items is appealing.

Other items that are just by themselves broken are fine also, but I would prefer to have them unavailable in the first playthrough. Keep that stuff in new game plus land.

That is because Une are the master race.

I tend to prefer the examples of Claimh Solais & the Death Ring as "broken" options. You'd still be limited by magic usage (for the former's special attack) and being forced to constantly dodge by equipping the latter (but the risk is clearly worth it).

Though I don't personally want it to get Crissaegrim/Valmanway levels of broken, I did have an idea for a powerful weapon in the past; a Wind-imbued spear called "Hræsvelgr". (I had the idea that this spear would be enchanted with powerful gales, enabling it to strike more than once per button-press, and it could create cyclones as a special attack)

Right, endgame stupidity to help you quickly grind out completion.

It'd be cool if there was a way to resurrect bosses and fight them again.

Now I want there to be an actual nerf bat near the end in game that attacks enemy levels rather than doing traditional HP damage.

I realized having a DPS weapon like the Valmanway with a drawback, like maybe, a one-of-a-kind multi-hit weapon that loses power, if you just blindly kill too many enemies could be fair. This way, there can also be more strategy for speedruns.

In my humble opinion, having overly strong weapons can take away from the atmosphere of a game. In this case, it ruins the "can our hero brave the odds?" vibe, eventually, for those that need atmosphere.

Back to what I was saying earlier about combos, even as a special prize, I felt that Soma's Chaos ring and Jonathan + Charlotte's Magus ring might make a new game + a bit too easy, as your magic regenerates like Majin Buu. Like, some may remember using the Alura une + Chaos ring combo for intense HP regeneration in Aria of Sorrow.

Heck, back when I was still doing competitive runs, I suggested to a TG ref that the Chaos ring in Aria would honestly take too much of the difficulty away to be an interesting speed run. Some would probably be all, "ugh..., he starts the run with the super steroid and never removes it. What's the point? There's so little danger with it that it might as well be a super easy 'hold your hand' mode."

Not trying to sound condescending to those who do like overpowered weapons, regeneration and combos, I'm just saying that some of us who do prefer balanced gear want to feel a sense of accomplishment, rather than having a thinly hidden free ticket to victory.