Statting an NPC concept

[Sindeloke]

My party is of variable, uncertain, and squishy size, so I'm giving them a DMPCish meatshield to haul around with them. Potentially she'll be available to any player who drops in for just one session, or possibly she could be run by one of the other players in addition to their own, so I want her to be pretty much RAW-compliant and easy to use, rather than taking too much advantage of DM fiat.

Trouble is, she's an established character who I can't see a way to make work straight off in 5e. Notably:

She's a meatshield, and thus needs to be survivable and have tools to protect the back line, but she's a former farmer with no access to good armor. Dex is a suboptimal solution, because her weapon of choice is a quarterstaff, and her race has a Str bonus.

She's closely bonded to her plowbeast, a homebrew domestic animal with the size and strength of a draft horse and the fearless, protective ferocity of a donkey. He follows her everywhere and is pretty comparable to an animal companion, but she herself has no particularly rangery traits otherwise, rangers have pretty minimal tanking support, and also they're starting at level 1.

Thoughts?

[archaeo]

Why not gently refluff Barbarian for this purpose? Fighter seems like it would work as well.

Otherwise, I'd honestly just suggest not worrying overmuch about providing a meat shield, or finding one that isn't an already established NPC. You're kind of painting yourself in a corner with this character, who you claim doesn't fit in the boxes the classes provide. Giving yourself more freedom will go a long way toward achieving exactly what you want. Alternately, simply eschew the DMPC idea and just go easy on your players for a few sessions until they've gotten out of squish territory and save yourself the trouble.

[Gurka]

I would suggest starting her as a barbarian (benefits from high strength, has the most HP, and gets CON bonus to AC while unarmored), and rather than going berserker or totem warrior, give her the ranger's BM archetype (with the proviso of allowing the beast to share her Rage at higher levels rather than spells).

I know it's not RAW, but I don't think it's a HUGE departure, and you're not going to find a lightly armored, strength based tank with an animal companion otherwise.

[Demonic Spoon]

RAW is that NPCs don't have class levels and you as the DM can do whatever the hell you want with an NPC.

Anyway,

-Hide armor could be sufficient and accessible to a farmer

-Is the plowbeast something that can be ridden? If so, you can have her ride the plowbeast. Give her the ability from Mounted Combatant which lets her choose who gets hit if someone attacks her mount.

-Give her unarmored defense like a barbarian.

[Shining Wrath]

Make her a Monk, so unarmored fighting is a natural. Add the plowbeast as an Animal Companion similar to what a Beastmaster Ranger gets. Subtract some of the Ki goodness of the Monk to compensate for having the Animal Companion.

[Ramshack]

I love the plowbeast Idea, I hate that you've pidgeon holed a tank into using a quarterstaff, as a DM if I was creating a tank NPC for my party id something like this.

She opens a trunk her father had kept in the attic of their small home. He used to be an adventure before settling down with a piece of land and raising a family. There she found his old suit of <insert suit of armor here> and a shield as well as his old blade.

I'd start any tank as 1 fighter,3 barbarian, take either the defensive style for another +1 ac, or protective style to help establish disadvantage on enemies attacking teamates. Her protective instincts are so strong that when a friend is threatened she goes into a frenzy (takes half damage)

After that you can continue with fighter or barbarian, or say she took an oath to protect her companions and go paladin etc. You'd get a second fighting style this way, either take which ever style you passed on before, or take duelist for +2 damage with a 1 hand weapon.

[Demonic Spoon]

You could also always give her some fighting-style-like-thing that gives her a couple bonus AC when wielding a quarterstaff.

[Sindeloke]

Thanks for the input, all. Looks like a refluffed barbarian is the general consensus; I was leaning a bit that way myself, and it would be pretty in keeping with the normal fluff to homebrew an animal companion subclass. It'd lose out on the sexy bear totem tanking benefits but this isn't a particularly high-op game anyway, and I can give the plowbeast some controller-y options that will help.

I may also either completely re-stat quarterstaffs (I've never liked that they're simple and have neither reach nor defensive properties, and the versatile thing is especially weirding me out this edition) or just let her have free Defense fighting style just because.

[Shadow]

Dex is a suboptimal solution, because her weapon of choice is a quarterstaff, and her race has a Str bonus.

The racial bonus almost negligible in 5e. The difference at higher levels will be nonexistant. The difference in the early levels will be -1 to appropriate rolls.
As for dex being suboptimal because of the quarterstaff, a monk can use all simple weapons with Dex.
So even a single level of monk on your refluffed barb can be built with dex instead of str and still work just fine with the concept you have in mind.
Between good dex, decent con or wis, and the barb stuff, you've got yourself a decent AC and defenses for the tanking even without armor (which fits your fluff) in addition to the stave concept.