Magical Girl Armorer Artificer BBEG

[Tokuhara]

So for a one-shot that could turn into a longer game, I wanted to flip the script on my players and have a Lawful Good BBEG, which for a while was going to be some standard "ends justify the means benevolent king" when I read Armorer and in a moment of humor said, "Yep, that's a Magical Girl class." So how would you guys make an optimized (in this case, make it a difficult but fun fight) Armorer Magical Girl? Say a 5, 10, 15, and 20 version, because I haven't the foggiest what range the game'll be

[noob]

One thing to know is that npcs do not need to follow the same rules as pcs.
So you could probably just do an artificier that picks its own spells and have no feats then compare it to other monsters with a cr equal to their level -1 and if they outperform them increase cr until they are at a cr where they are in line with other monsters an if they are weaker lower the cr until you find monsters it compares to.
As you know npc wizards have like 2+ cr less than their equivalent level and npc archmages have 6 less cr than their equivalent level but that is due to spell selection.

[bendking]

Perhaps not the answer you were looking for, but first off - the Armorer subclass isn't great for dealing damage. It can either be a decent tank with a taunt mechanic or a mediocre range damage-dealer.
Secondly, it's still an Artificer, which is a bit of a support class, which might not fit a BBEG that well.

If I were you, I would probably use an Artillerist as BBEG instead, and just flavor her as a magical girl.

[noob]

Perhaps not the answer you were looking for, but first off - the Armorer subclass isn't great for dealing damage. It can either be a decent tank with a taunt mechanic or a mediocre range damage-dealer.
Secondly, it's still an Artificer, which is a bit of a support class, which might not fit a BBEG that well.

If I were you, I would probably use an Artillerist as BBEG instead, and just flavor her as a magical girl.

A bbeg with support abilities can work great knowing kings can surround themselves with competent servitors.

[Tokuhara]

I hadn't fleshed out the fight 100%, but I did plan on having her have mooks (Goblins reskinned as fuzzy cute woodland creatures in pastel colors that would cause migraines to mere mortals) so her having support abilities would be great

[Unoriginal]

My advice is: don't build a boss like a PC, it most likely won't work well. Compared to NPCs, PCs are squishy, but hit harder and have tons of abilities that'd be overengineering for a NPC.

Simply assigning the stats and abilities you want based on the "create a monster" section in the DMG will give more satisfactory results.

[Incorrect]

Would it be worth it to use the Infiltrator Lightning Launcher with Sharpshooter?
Its still not super impressive damage...

But sniping with that from behind a wave of meat shields, might be fun?

[Silpharon]

I'm looking at an Armorer X/Psi Warrior 3 multiclass. With haste and sharpshooter I think the ranged damage of the Infiltrator is decently good, and can be excellent with some multiclassing.

At 20 with Haste, assuming first attack without sharpshooter, then with sharpshooter and avantage for subsequent hits:
70.5 avg damage per round
118.5 avg damage for action surge round

I'm looking at a 1 level dip in Genie Warlock as well, which allows for some fun games of getting Haste and Bless (through Spellwrought Tattoo infusion) without concentration once per day with Glyphs of Warding in the Genie Vessel. Then if you can get a Ring of Spell Storing, you can get another creature like a homunculus servant to concentrate on Elemental Bane (thunder). The Genie Djinni damage boost procs the bane damage. This frees you up to concentrate on Hex. I'm also going Keranos as my deity in MoT, which gives a limited supply of +1d6 lightning damage on 1 attack per turn. All this combined I'm at:
97.5 avg damage per round
152.5 avg damage for action surge round

I can also stick shatter in a Spell Storing Item and upcast Tiny Servant at 5th level for 5 servants. Then my bonus action will do 102.5 avg thunder damage (5 turns of a tiny servant with shatter and elemental bane). I can do that twice a day. So per round damage bumps to:
200 avg damage without action surge
255 avg damage with action surge

Fun times.