Setting up an Ettin?

[Lazy_Perfectionist]

Here's a few brainfarts.
Scroll to IDEA to skip my though process and go straight to my suggestion.

High strength, right?

Hands:
Three Main Gauche of Parrying = +12 defense. A length of zero means no attack penalty.

Three Duskdaggers. Again zero length, but now with armor negating. Leaves the ettin vulnerable, though.

three snake bladders- poison stacks. If a character can dodge attack, just one snake bladder stacks very quickly. Three? Just get yourself some PR.

Gloves of the Gladiator + Sword of Quickness + Boots of Quickness: 12 attacks a round.

Heads:
2 Horned Helmets (adjacency?) two more attacks, 4 with quickness.

If you don't depend on boots of quickness, but have a mage cast it, then you can equip Chi Shoes, or Boots of Stone.

Obviously, regeneration is a big plus, but continuing along atheme..

Stone Bird.

Exact stats of Ettin can be found in Edi's database "Base U" worksheet, no 488.

So, lets refine this a little.
3 Snake Bladder Sticks - gains no benefit from Ettin's strength. It's out.
Armor - it's just going to be hard to protect from counters, so Elemental Armor, while tempting, is out.
I'd go with either the Shroud of the Battle Saint (flaming weapons and attack bonus), Marble Armor, Stymphalian Wings. Monolith armor would be nice, as would Robe of Shadows, but they are out. Hydraskin Armor has some potential, with regen.

IDEA

So, the following build will have some obvious weaknesses, but is an extreme idea you could tamper with some practicality.

Supporting Spellcasters will cast the following, at minimum:
Luck, Iron Warriors, Regeneration, Berserkers, Quickness, Flight, Mist, Fog Warriors.

1 Gloves of the Gladiators for 4 attacks (8 w/quick)
1 Duskdagger, to handle unusually well protected units.
1 Shroud of the Battle Saint with a fire or nature bless, or Hydra Skin Armor
2 Horned Helmets
1 Chi Shoes
1 Stone Bird

So, with this setup, before quickness you get
4+1+2+1+4= 12 attacks. Facing a defense 40 unit? the last attack comes in with the defender penalized 20 points for successive attacks. If flaming weapons is included, you also get a couple of fire damage, though I don't think that counts as another attack.

After quickness has been cast, you're generating 24 attacks a turn.

Obviously, there are some changes you can make to increase survivability, but this is the extreme version. It will the Ettin to survive if you have some other large units around.
Switch to three Main Gauches of Parrying, and you get +12 defense, and instead of 5 attacks from arm slot weapons, 3. So, 20 attacks after quickness is cast? Not a huge loss.