Though I do agree to wanting to see some of these mechs in game.
King Crab is one of the very few mechs that is -- in terms of Lore -- supposed to be able to use the Devastator AC/20 (the only single shot AC/20 to exist, as all others are multi-shot akin to the two demonstrated here using MWO's resources) without having to brace and stand perfectly stationary. (Even the Atlas had to, and the book this was in the Atlas pilot still lost his balance, giving the Devastator a 'No Go' from Steiner forces since it carried bad risks with its intense recoil).
Mechs which Meatwagon here described as "Crab-like" (as in like the Crab mech) are known for being very short compared to other mechs of their weight class. In exchange they have very long phallic or saucer-like bodies. (Think Stalker, but no taller than the Hunchback in regards to the 'Crab'.) These are especially vulnerable from the side and the top but very hard to hit from the front (phallic rigs like Crab mech, old art King Crab) or mostly vulnerable from the top while low-profile from the side (new art of King Crab). Either way, crab-like mechs are supposed to be hard to hit from either the front or the side due to their shape, being smaller than other mechs of equal tonnage, but in exchange they are severely at risk of LRM-induced death due to their very huge top-down profiles.
For example, despite being 100 tons the King Crab would be no taller than just below the Jagermech's arms. However, two Catapults could probably stand on top of it front to back (old art) or side by side (new art). It just depends on whose art you go by. (Old art, the King Crab is as long front-to-back as the Victor is tall, which is longer than a Stalker is from back to nose).
It is because of this low-to-the-ground body-shape, however, that the King Crab can -- in lore and tabletop-- use the Devastator 203mm variant AC/20 when the same gun is supposed to be impossible for a Jagermech to use (despite all the AC/20 Jagers).
The Cauldron Born uses one of the very few UAC/20 variants that fire 20 damage/shell rounds. Something that if mounted on a humanoid mech (tall and skinny in comparison) would be impossible to manage while moving.
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Now as some might ask, what about all the AC/20 totting mechs like the Hunchback? Tabletop focuses its damage in one spot!
The 4G Hunchback carries the Tomodzuru Autocannon Mount Type 20. That is depicted in multiple concept art as having 4 rotating barrels within the Hunch, firing a series of 4 cannon rounds each doing 5 damage in a rapid burst dealing 20 damage.
In this video it is depicted as firing 5 shots (without much recoil though it's noticeable). That would be a Defiance Mech Hunter AC/20 variant. (5 shots, 4 damage each).
Some others with specified shot counts:
ChemJet Gun - Slow 3 shot burst, 185mm, vicious recoil.
Armstrong Requiem - rapid 6 shot burst
Crusher Super Heavy Cannon - 10 shot burst.
There's 15 total (9 unique, 6 variants of variants) AC/20 variants.
One of them shoots 100 bullets to deal 20 damage.

(Note: There's multiple manufacturers of Chemjet Gun and Crusher, these are supposed to have minor variations to include 'MG' style versions. An example of the Crusher in an MG version, the firing rate is slower, generating 10 shots across 4 seconds instead of in a rapid burst, much like a series of 5 AC/2s but for only 14 tons. Lore-wise its recoil is manageable and would have half the regular AC/2 range, with no cooldown time. Downfall is that this exists only in the lore but in tabletop all AC/20s are summarized to hit a specific component for mathematical simplicity.)
For comparison, there's supposed to be 44 unique variants of the plain old medium laser. It's over 60 with variants of variants.
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But back on topic, in the not too distant future I think these would be a lot of fun to include. Four legged mechs are supposed to have a much easier time climbing and be able to maintain their balance against knockdowns that would take down somewhat larger two-legged mechs.
Edited by Koniving, 27 July 2013 - 09:22 PM.