I'll try to answer the OP from another angle:
In RPG-ish campaign gaming, or from an in-universe viewpoint, you need to consider the size of your force. Is the lance built for a specific task (e.g. Fire Support for A company), or is it a generic vanilla jack-of-all-trades unit thought to operate on its own?
Based on the latter approach, the typical un-specialized all purpose lance consists of one "Anchor", one "Scout", and two "Brawlers":
- The Anchor is the heaviest (but typically also slowest) of the bunch, and combat-wise, the core of the lance. When there is trouble, this is the mom all others run to. Expect it to be a bodyguard unit piloted by a grizzled veteran Sergeant.
- The Brawlers are versatile medium 'Mechs that can outrun what they don't outgun. The unit commander will typically ride one of them.
- The Scout is just that. Stressing mobility over firepower or armor, it's not supposed to engage the enemy on its own but can be used for flanking or harrassing in a combat situation. Typically, your lightest 'Mech will end up in this role.
A very generic Lance that could be found virtually anywhere as of 3025 might, for example, look like this:
- 65t Thunderbolt (Anchor)
- 55t Shadow Hawk (Commander)
- 45t Phoenix Hawk (#2 Brawler)
- 20t Locust (Scout)
Assign them any mission and they will likely get the job done.
(Ok, just for kicks I tried to turn the idea on its head and came up with this Kurita lance: Panther Anchor, Dragon Commander, Jenner Brawler & Charger Scout... but I digress :) )
For a company that is operating as a cohesive unit, as opposed to three stand-alone lances, you just scale up the idea. Scout 'Mech becomes Scout Lance (either four similarly fast 'Mechs, possibly the same 'Mech four times, or an overall fast recon lance that still has the aforementioned sub-structure among its individual members); Anchor 'Mech becomes Combat Lance; and the Brawlers become Command or Fire Support lances.
At the company level, it might be feasible to include specialized units (like the Raven for ECM, a Rifleman for air defense or a Cyclops command 'Mech) that would be more of a liability if they had to perform in a standalone lance.
You can scale this up from three companies performing distinct roles in a battalion that operates as a cohesive unit. But my pesonal impression is that companies are the largest formations that can be assigned a meaningful individual battlefield role.
(Note: I reckon a 'Mech lance is the equivalent to a real-world armor platoon. As a Luftwaffe guy I don't have any real-world experience with tank operations whatsoever though. If a veteran with actual experience has a different opinion, he or she is probably right.)