There has been a lot of debate on the balance of clan weapons vs IS weapons. For the most part, it terms of damage vs heat, they don't seem too bad to me at the moment.
However, one aspect of balance that tends to get ignored is the critical space and tonnage requirements of clan weapons. Doesn't seem like a big deal does it ... so they aren't as heavy and don't take as much space ... doesn't seem like much of an issue.
Clan ferro and endo take 1/2 the critical spots of IS version.
Clan heat sinks only need two critical spots.
The result of this is that, even considering fixed equipment, the clan mechs will often have significant pod space and tonnage available for weapons.
Which leads to the following ... at the moment, I have exactly the same weapon loadout on my 55 ton Stormcrow as I do on my 85 ton Stalker. The Stormcrow moves at 100kph, while the Stalker is about 60kph. The Stormcrow has an XL engine while the Stalker has a STD one (since it would die much too quickly with an XL). Obviously the Stalker has more armour

The observation is that even if the weapons are balanced, the lower weight and critical requirements for clan weapons means that ton for ton the clans can generally carry more firepower.
Some clarifications ...
1) I do not want the clans to be the same as IS
2) I do want to see a reasonable balance
The best way to achieve that would seem to me to be an across the board buff to IS mech structure (on the order of 5% to 10%). IS mechs would then be more durable while clan mechs would have the firepower advantage. Underperforming clan and IS mechs could be further tweaked either using quirks or other approaches.
Thoughts?