Actually, many of the original 16 Clan OmniMechs were actually fairly well-armored, in addition to generally being faster than their IS counterparts.
The
Daishi carries 19 tons of Standard Armor (99% of maximum).
The
Gladiator carries 13.5 tons of Clan FF Armor (88% of maximum).
The
Masakari carries 13.5 tons of Clan FF Armor (98% of maximum).
The
Man O' War carries 11 tons of Clan FF Armor (85% of maximum).
The
Mad Cat carries 12 tons of Clan FF Armor (100% of maximum).
The
Thor carries 9.5 tons of Clan FF Armor (84% of maximum).
The
Loki carries 8 tons of Standard Armor (61% of maximum).
The
Vulture carries 8.5 tons of Clan FF Armor (81% of maximum).
The
Ryoken carries 9.5 tons of Clan FF Armor (98% of maximum).
The
Black Hawk carries 10 tons of Standard Armor (95% of maximum).
The
Fenris carries 7.5 tons of Clan FF Armor (94% of maximum).
The
Dragonfly carries 7 tons of Clan FF Armor (98% of maximum).
The
Puma carries 6 tons of Clan FF Armor (97% of maximum).
The
Uller carries 4 tons of Clan FF Armor (72% of maximum).
The
Koshi carries 3.5 tons of Clan FF Armor (75% of maximum).
The
Dasher carries 2 tons of Clan FF Armor (55% of maximum).
Outside of the
Loki and the three lightest TRO 3050 OmniMechs, the vast majority of the Clans' initial Invasion OmniMechs are at or very near their maximum armor loads.
In fact, only two of the 16 carry less than 70% of their maximum armor load: the 65-ton
Loki (61%) and the 20-ton
Dasher (55%) - with the former devoting ~43% of its total mass to OmniTech pod space (allowing for substantial and flexible armaments) and the latter carries a massive engine (for a base maximum speed of ~162 kph, going to ~216 kph with MASC activated).
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IMO, one of the better ways to "balance" OmniMechs (both Clan-built and, eventually, IS-built) against non-OmniTech BattleMechs is to implement the canonical OmniMech restrictions (described in more detail on pages 47-57 of
TechManual).
- An OmniMech's internal structure type (standard, endo-steel, etc) and location/distribution of criticals cannot be changed.
- An OmniMech's engine type (standard, XL, etc), rating (250, 300, etc), and location/distribution of criticals cannot be changed.
- An OmniMech's armor type (standard, FF, etc), amount (total tonnage/number of armor points), distribution (how much armor is where), and location/distribution of criticals cannot be changed.
- The locations and types for the cockpit and gyro may not be changed.
- The presence and location(s) of MASC and TSM cannot be changed; neither may be added to an OmniMech that wasn't originally built with it, and neither can be moved into a set of criticals other than what they originally occupied (for example, it may not be moved from the Left-Torso to the Right-Torso).
- The type of heat sinks (standard, DHS, etc) that are equipped on an OmniMech cannot be changed.
- Weapons and other pieces of equipment, additional Heat Sinks, Jump Jets, and other items may have been built-into the OmniMech as hard-wired "fixed items". Examples of such fixed components include the Flamer on the Adder/"Puma" (mounted in the Center-Torso), the Medium Lasers on the Avatar (mounted in the Center-Torso), and five of the Jump Jets on the Summoner/"Thor" (one mounted in the Center-Torso, the other four filling the legs). Such "fixed items" may not be either moved to another location on the OmniMech nor completely removed from said OmniMech.
In exchange, each open critical slot could be a non-type-specific hardpoint, or each configuration (that is, "variant") could be assigned a number of non-type-specific hardpoints (based on its initial loadout).
This would allow PGI to implement multiple OmniMechs of the same weight while also keeping them relatively unique (so that there is a reason to take "OmniMech X" over "OmniMech Y" beyond "best geometry/hitboxes").
The above restrictions are a large part of what keeps each OmniMech unique in spite of their relatively flexible weapon and pod-mounted equpment loads (e.g. why a
Blood Asp might be used in place of a
Kingfisher and vice versa, as well as why the former exists in the first place despite being predated by the latter by 172 years in-universe, and why OmniMechs of the same tonnage can exist without just being "X-ton gunbags with different skins").