Nearly all artworks of Cherche in general have her with it, including all three attacking portraits, so Helswath is just an eventuality at this point. Plus she has been slipping on the tier list so now more than ever she should get it. Having been using her for a good long while (even briefly before SI came out) I have some suggestions.
My first and favorite idea is thus: unrefined it has def+3 and a Slaying effect. Simple but not spectacular, can always be refined for a stat buff and used on defense if wanted to however. Effect refine cuts it's mt. to 11 and spd drops by 5 and it's given a Brave effect. With this, she gets more fire power for her preferred play style and she gets flexibility in terms of specials and seals, with 3 more defence as a bonus. She can get one round Glim/Bows with any seal or one round Bonfires with HB seal (or even Galeforce). Otherwise she can run Ignis like she currently does with Bonfire.
"Why the slaying effect" you may ask; well IntSys adds weapons with refines as well, she needs some basic default Helswath before she refines it. The other big reason is that speeding specials up and launching them every round has been pretty much the meta recently. I mean look at all the skills and weapons based on this concept; Steady and Warding Breath, Flashing Blade, Heavy Blade Seal, Felicia Plate refine, Bold and Vengeful Fighter, Wrath, and Slaying Weapons absolutely EVERYWHERE, even on units who have legendary weapons but prefer a basic stat refine. Cherche can capitalize with HB seal but mostly with just Glim/Bow and maybe Galeforce.
On that topic though, what if Brave weapon Helswath IS the default? Well I still will suggest by default it gives def+3, and when refined, it gains Meisterschwert's effect of Brave during both phases. This maintains the idea of "can be built for both phases" like the last one but to a whole new level. My concern though is that she has poor res unlike Rein and she requires Iote's for a DC set, so no Distant Def seal.
A random idea I had (before Forblaze refine was shown I preface) was by default it has Death Blow and when refined it gets a Brave Effect. Or these can be swapped. Brave Weapons and DB are practically made for each other after all.
I'm not sure what's more broken, spamming the hell out of Bonfire or Moonbow with a massive atk stat, or spamming just Glim/Bow with HB seal and an even more massive atk stat.
Either way these are just a couple ideas I had along with my thought process for each. You decide if they're way too broken to be considered.
I think that Meisterschwet's broken effect will be unique to Rein, as it is way to powerful to become a common wpn effect. About brave effect +3 def; it would be totally possible, like Amiti but woth a def instead of a speed bonus; but adding Death blow to the weapon, to a brave weapon would be too good to be true, and irrealistic.
I've personally used Desperate Assault Cherche, and while she kills several more units she would otherwise struggle with, it's a lot trickier to set up since it relies on either her or someone else w/ Reciprocal Aid living a hit. She also loses out on Hit and Run which is part of the beauty of using her; you can very easily mitigate her enemy phase weakness.
And I agree, though on the whole I still agree with the majority of the placements
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