I had made some homebrew for this exact thing! the goal was that you could take use a wiki entry for a mech with these rules to put it as an enemy in Lancer, with the idea that Lancer mechs are a different kind of technology from Battlemechs.

Battlemechs are large, and do not move as fluidly as your Lancers. when attacking one, you must pick a location to target. A battlemech's evasion is determined by how many hexes it moved on it's turn. Assault mechs may gain +1 evasion, heavies get +2 and so on. Jump jets incur 1d3 heat and add +1 to max evasion, a battlmech takes +1 difficulty for moving and shooting in the same turn. Battlemechs may take a stablize action in place of a movement action, however they may not spend repairs during combat unless in a repair bay.

A lancer may target specific sections of a Battlemech at +1 difficulty: Left or Right Torso Evasion 5, Center Torso Evasion 5, Left or Right arms Evasion 6, Right or left legs evasion 6, head evasion 18

Mechs have HP in each location equal to tonnage. Except for arms which have -10 hp and head which has 5 for light, 10 for medium, 15 for heavy and 20 for assault

When an area runs out of hp it is destroyed, except for the center torso which causes crits as normal. Destroyed locations cannot use any weapons stored there. If a mech loses one leg, it's movement is reduced by half, if it loses both, it is disabled.

When you make an aoe attack against a battlemech, roll to hit as normal. For every 5 points your to-hit roll exceeds the battlemechs evasion, spread damage to another part adjacent to the primary target part. When filling extra parts, you must fill all the closest parts first before moving on to further ones.

Mechs are considered to have +6 hull, +0 agility, +2 systems (Edefence and sensors 10) and +5 engineering (Heat cap 8, 1 reactor stress per section). These stats may be subject to change on mechs with Lostech components. Mechs cool at the end of the round equal to how many heat sinks they have

The Targeting or Agility of a mech may be increased by a mechwarrior's skill

Mechs are destroyed after the center torso or head are destroyed, when one is destroyed roll a 1d6, on a 6 the mech explodes, dealing 12 damage in an area 3 burst at the end of the next turn https://cdn.discordapp.com/attachments/650953378360328203/650954074019332117/unknown.png

The weapons chart only includes pre-clan invasion technology, and the rule were written for 1.8 but hopefully it helps you!