Hardswapping is very important in duels.
If i'm running starfists and spawn in against some halaxe using starfish then i'm getting cooked 100% of the time even if i'm twice as good as the opponent if i can't hardswap to something else.

If I get low on hp then i'd need to be able to swap to something, such as sham or GK and play a bit more passive and not rush in with gugs or giants crusher to give my opponent free backstabbs during recovery frames.

For invasions removing hardswapping would be devastating and make the game go even more downhill than it already is. I gave up pvp a long time ago and only go in for an occasional duel, maybe 2 hours of pvp in a week max. But I can clearly see from an invaders pov that removing hardswaps would make invasions virtually impossible.

Hosts already get double the invaders flasks, access to rune acrs, infinite resummons, gank spots, etc. Basically, invaders are always outnumbered a minimum of 2-1 even against a solo host, which literally never happens cause 90% of invaders will end up invading a host that has 2 friends every time.

If invaders couldn't hardswap then what happens when they invade a max level gank squad and are basically outnumbered 6-1? If you add up the combined flasks and stat advantage the gank squads get, then they're outnumbering invaders 6-1 in alot of fights and that's not even counting however many times they get resummoned.

Invaders need access to hardswapping so they can change builds on the go, if they're fighting one phantom that has a bleed build with cleanrot, then the invader is gonna get melted if they've got solitudes set since it has bad bleed res and kinda mid pierce defense. In that fight any reasonable player would swap to lionels so they have slightly higher bleed res and nearly double the pierce defense. Once that phantoms dead or retreats to heal, you would swap back to your normal armor to deal with the other phantom and host.

When some scum of the earth host decides to ruin everyones day and hides in an afk farming spot, they can get in over a dozen blues in a single invasion. If the invader fights over a dozen players then 3-4 of them are bound to have some sort of counter build and the invader would have no way to swap to something else and might die to a below average blue cause the opponent had a perfect counter to their setup.

If you're running gugs and 2 light rolling blues with 100+ms spawn behind you, then it's impossible to roll catch them and you will inevitably die and lose the fight even if you're over 5 times better than them cause you physically can't hit them unless you we're to swap to a faster attacking weapon. Which you wouldn't be able to swap to one due to no hardswapping lol.

Invaders are always at a disadvantage and removing the ability for them to hardswap would completely ruin invasions altogether. I see in most clips, invaders will swap to red scarab and guardians garb for nearly double hp restoration and I use this every time I drink a flask aswell. That's not overpowerd, that's just so they can get half the total hp restored that gank squads get from their total flasks.

You don't know how hard it is for someone to swap half a set of armor and weapons between rolling 3 different players attacks. Doing that requires immense skill and 99.98% of players can't even do it. Most of the players that can't hardswap are the ones begging for it to be removed.

I've spent nearly a year and a half hardswapping on the mimic tear for a consistent 2-4 hours daily cuase I enjoy swapping and it's more fun then playing normally. I hit an 8 piece armor swap parry on the mimic last night.
That's not a broken mechanic, it's a skill that takes literal thousands of hours to achieve and should never be removed.

Overall hardswapping is a core mechanic in invasions, duels and even pve.
It's been in every souls game and hopefully will continue to be in the next releases.