For most of the game, I've been running a staff on the left, with the Moonveil on the right. And the MV is great, but I don't think it's the best late-game magic sword. What's handy about it is that it packs wicked damage with its stellar INT scaling and features an AoW that offers a mix of great poise damage, excellent magic damage, great speed, and very high FP efficiency - and that's in addition to the extra reach it has casting that little beam. And you can get it before you even attempt Stormveil Castle. Between that AoW and just using the katana moveset with the incredibly solid INT-based damage scaling, you don't even need to cast for the first half of the game. Straight-up just wap em and spam the AoW. Grab a magic uchigatana to powerstance with and obliterate enemies with a mix of nasty bleed and magic damage. Nice to have if you aren't explicitly pushing to later areas to get the spells, talismans, and physick tears to make casting truly viable early. It's quicker to get the Mooveil and just wreck the first 3 regions with it.
Thing is... in terms of actual damage output and versatility... there are better weapon options. I've been tooling around and there are some DEFINITE overlooked options.
The first is the simple magic uchigatana. With the Carian Grandeur AoW on it, it is absolutely superior to MV AoW. It's not quite as fast, but has far more range, does yuuuuuuuge magic damage AND poise damage, and charges through 3 stages. Stage 1 is already massive. Stage 3 is nuclear. With the sorcery options you have for breaking poise, you can utterly decimate bosses with a fully charged carian grandeur swat. It even does increased damage when poise is broken. Like... imagine stacking the damage of 2-3 crits with one AoW move. Thousands of points in damage in one fell swoop - knock off almost half of a colossal boss's bar in one attack. It's honestly absurd how good it actually is. All that you have to do is break bosses' poise with your sorceries and then issue sweet, vertical justice upon them with a giant magic bonk. Get it before reaching Margit, drop him with the shackle, and watch more than half of his HP vanish from just one charged Carian Granduer. It's shockingly good.
Geez... strategically you can put say, Loretta's Slash on a scythe - it comes off quick with a lot of poise damage while providing iframes that keep you safe in the fray. You could chain it to the end of poise-breaker spells like rock sling, gavel of haima, greatblade phalanx, etc and literally smash the poise of just about any combatant in the game before they can get anything off. Like... you can cancel 2nd form transformation sequences. You can just keep chaining the poise breakers and keep high level bosses neutralized for the majority of fights. Tuck a second magic scythe in the staff hand and you can swap to proc bleed and alternate between dishing out disgusting magic attacks that continually break the poise of even the heaviest enemies, and shredding them down to bleeding piles while they lay helpless.
I mean, compare these possibilities with something like the Darkmoon Greatsword. That thing is cool and powerful, but I do think with the somewhat slowed greatsword attack speed, frost buildup instead of bleed, average poise damage, and basic projectile AoW (don't get me wrong, I see the damage and speed,) it's kinda... pedestrian. There's nothing special about it. It's just good, cool, and strong. Actually fighting with it all of the time just gets boring.
The one that really intrigues me is the Wing of Astel. I think that it might be majorly underrated with its AoW, Nebula, which casts a wide-reaching gravity blast. This is great because it amounts to pretty big AND wide (like ~180 degrees in front of you) physical damage that scales from INT. If your only damage stat is INT like me, you run into trouble facing enemies with high magic resistance, which this AoW shreds. It also deals nasty poise damage. And then, IN ADDITION to all of this, you get ANOTHER unique attack in the charged R2. It's a ranged magic projectile attack that's actually strong, can fire in succession, and costs no FP. And then it is a curved sword, so it has a great moveset, including that little charged-attack-cancel-roll. So all in all, it actually seems quite good as an evasive/defensive weapon to go with offensive spells.
The main downside is that its plain attack damage isn't the best. But late game, who cares? I have plenty of FP. At least regular attacks hit for 20% more damage on gravity types - handy for more than one late boss. It doesn't need to be the best possible pure melee weapon, though - just serviceable for the weaklings. There are better class options than pure INT for melee. And yet, many of them can't quite break poise like your litany of INT-scaled sorceries can. I can only imagine a sorcerer would want to have many ways to neutralize threats and control the battlefield in order to make time/space to cast heavy-hitting spells. Like, ultimately I wanna melt you with Comet Azur, Meteorite of Astel, Stars of Ruin, what have you. Might even go for Carian Piercer... which I tend to think is also underrated AF with scaling, nearly 3x multiplier on my Carian Regal Scepter, which has ~350 scaling at 80 INT... do the math on that damage, it's also pretty nice for smashing poise, though the attack itself is slow to set up.
The melee weapon will always pale in comparison to what those do for an INT character - so for me, choice of melee weapon isn't about the plain melee attacks, but strategies that type of weapon affords. What is a sorcerer's worst enemy if not a fast-dodging, distance-closing, swift-attacking foe? And what does the sorcerer most need to deal with that? Surely not a big enough sword to bludgeon them with... but rather an effective way to stymie their speed and reactivity. Wing of Astel does that very well, as the half-circle wave of gravity goo it shoots out hits continually on contact and staggers, giving you time to start either chaining poise-breaking AOE like the gavel of haima or just hitting them with a strong carian sorcery all charged up... or back up and pop a strong ranged sorcery the moment the AoW beam begins traveling out. Dang, hold onto the magic uchi and switch to that to bring out the Grandeur.
I mean, it kinda just puts everything in front of you in the mire of a gravity magic torrent. Gets you out of trouble when enemies overwhelm you and you don't have an AoE sorcery active right in that moment, probably kill half of weaker mobs as you roll back. With so many ways to get out of the fray, break flow, and dish out nasty damage, there's no reason to stay there swinging a sword around and getting poked in your squishy mage parts. Better to have a sword geared towards controlling the battle than one who's main virtue is in the AR it produces. Scale vigor to no more than 40 and invest points in mind to always be using your magic abilities.
Thinkin bout that Wing of Astel. Might give it a shot. I think it's going to be quite advantageous paired with the right spells and talismans. As far as 'special' (locked AoW) magic weapons go, it might just be a sleeper top-tier option for a spellsword leaning more towards spells.
I mean, I'm approaching level 150, and have capped INT, so I can even add DEX as a secondary to speed up casting abit and make up for the melee damage loss. I think it's gonna be my best bet against bosses like Maliketh or Melania.
Also been rethinking my spells. For the most part, the standard glintstone/blade sorceries more than suffice. Hell, 90% of the time, the humble rock sling is kinda the meta, if there could be such a thing for PvE. Truth be told, there are a lot of options for late game. Even spells that seam weak for most of the game become clutch as fuck when you have 80 INT and an appropriate staff. The snowfield opens up some good stuff, too. I've never messed with spells before this build, so I'll have to read up and play around abit. One spell that is REALLY kinda shocking me is Crystal Barrage. It's a press/hold style glintstone projectile beam, like a tiny glintstone version of Comet Azur. The damage is unsuspecting when you first buy it from Sellen for a meager 1500 runes, but late game it quickly stacks damage AND staggers on each little peck. It is actually more useful than Comet Azur, and respectably strong for the low FP cost.
'for the reasons you mentioned' 
