Within the parameters you have dictated, no methods exist within RAW

The specific rules you have already highlighted in your question, being the core rule in the remove curse spell, and the specific exception on the Sword of Vengeance. This cited question, unfortunately, chooses to cherry-pick the phrasing of SoV in a misleading way, leading one to infer that there is precedent for remove curse being able to eradicate a curse from a cursed magic item.

The general rule is that a cursed item is always cursed. An attuned creature has the item's curse extend to them, and casting remove curse on that creature gives, at best, a brief moment of relief before the curse is instantly re-applied. Casting remove curse on the cursed item breaks its attunement, ending the curse on the creature but not the item.

The only "exception" to this rule doesn't even involve removing the curse, but rather using banishment to rid a SoV of a vengeful spirit that is the source of the curse. The specific ruling on SoV overrides the general rule in that instance alone. There is still no precedent for the remove curse spell or any similar effects being able to rid a cursed item of its curse.

Unfortunately, wish and divine intervention remain as the only permanent RAW methods, as you have surmised.

This is profoundly unbalanced as written. During downtime days, as written, the item permits the user to pour unlimited numbers of hit dice into the bracers. All you have to do is ensure that you don't end the day with less than half your maximum number of hit dice, and that you finish storing at least an hour before you go to sleep, and you're losing nothing for the next day. You can then tap those whenever you like for major blocks of healing and/or curing the blinded/deafened/paralyzed/poisoned conditions.

The cost of storing is meaningless because no one's going to take the Store action while in combat anyway. There's no reason to, and actions in combat are far too precious to spend unnecessarily. If they're safe enough to store, then the couple of rounds won't matter. Spending a die to cancel the debuff is if anything even more pointless, because then you're burning the die you just stored in order to get rid of the (minimal) side effects of storing it. Between that and the action cost, it means that you're effectively burning a hit die and two actions in order to give yourself a durability penalty for a round while in combat. It's just a terrible idea all around.

In order to have any hope of being balanced, there needs to be a serious limit on how many hit dice can be stored in the thing. Either there's an explicit cap, or the hit dice that are stored in the thing simply don't refresh while stored. The way that gets handled is going to be a significant part of how balanced it is and for what rarity. When the answer is "there is no limit", it breaks the HP economy and therefore cannot be balanced. None of your proposed fixes address that core issue in any meaningful way, and therefore none of them are particularly pertinent here.

For where to put the hit die cap, if you want to go that route? Well, the ring of spell storing is an attuned rare item (a very nice attuned rare item) that can store up to 5 spell levels in a somewhat similar way. Those spell levels could be healing spells (but generally aren't). Figure out how much healing you could reasonably get from packing one of those things full, and that's a floor... because the ring of spell storing is way more flexible than that. For another benchmark, compare it to the max cap of the staff of healing (using only 9 charges rather than 10, because you don't want to risk a 5% chance of it just vanishing). That, too, is an attuned rare item, and its ability to heal others makes it somewhat more flexible, but it's getting closer. The "staff possibly vanishing" and "only cleric/druid/bard" aspects bring it down a bit.

As a sidenote, by my understanding of Brandon Sanderson's work, this sort of thing may be a recurring problem with trying to convert his ideas into magical items for 5e. 5e is pretty careful about not letting things break the system. Sanderson is all about having people take the powers they have access to and figure out ways to use them to break the system. The two philosophies don't mesh particularly well.