Mechwarrior

Alright, mod recommendations.

1.) Coyote's Missions - Adds a number of new mission types, such as Duel, Attack and Defend, Beachhead Defense, Battleground, Ground War, Rescue, Convoy Destruction, and more. The mod also adds a variety of additional modifiers such as aerospace fighters, either as allied units that can be acquired through a special Aerospace Capture mission type that will randomly appear in certain systems, or as high-tier enemy units that will sometimes appear as randomized mid-mission modifiers. Also allows you to disable certain mission types (including the base game contract types) from appearing via Mod Options if you dislike any of them.

2.) Star Map Mouse-Over/SMMO - A quality-of-life mod that just lets you mouse over nearby systems in the starmap to see additional details about the contracts available there, such as who's offering the contract, who the target is, the max tonnage, the difficulty, et cetera.

3.) Better Mission Choices - Allows you to change a variety of parameters regarding how contracts are generated via Mod Options, such as the amount generated per system or the percentage chance that certain factions will offer them versus others.

4.) The Known Universe - Modifies the Starmap to match Sarna and MegaMek's starmaps for a given date, as well as adding every single canon system and every single canon faction with a noteworthy starmap presence (and combined with Better Mission Choices, will allow those factions to offer contracts to you in conflict zones or be featured as targets). Want to fly out to the Clan Homeworlds during the middle of the Succession Wars for some fucking reason? This mod will let you. The Known Universe also lets the Starmap progress past 3049, all the way to 3152. Do note that enabling this mod, loading a save, and then disabling this mod will break the starmap for that save, so if you aren't sure about this one but want to try it I recommend making a copy of your current save or starting a new save just for it.

Other BattleTech games to try:

1.) BattleTech 2018 - A similar experience to MechWarrior 5 but in Turn-Based Tactics format, where you fly around the Rimward Periphery and southern Inner Sphere managing a mercenary company. However, the story for this one plays a much greater role in the experience, and unlike MW5 the story is actually pretty great, so I won't spoil it. It also has a healthy modding scene like MW5, with two big main mods: BattleTech Advanced 3062 and RogueTech. While personally I still like the mission-to-mission gameplay and more sandbox-focused nature of MW5 more, I recommend trying this game even if you aren't super keen on Turn-Based Tactics, the story and presentation alone are worth your time.

2.) MechWarrior 2: 31st Century Combat, MechWarrior 2: Mercenaries, and MechWarrior 4: Mercenaries - The OGs. These games are all abandonware and can be easily acquired for free. MW2 runs great in DOSbox, while MW4 runs on modern systems, though some coaxing (compatibility mode) may be necessary. MW2 is widely considered to be one of if not the greatest mech game ever made, while MW2 Mercs is an expansive (albeit very buggy) experience. Ghost Bear's Legacy sucks, don't play it. MW4 Vengeance and MW4 Black Knight are fine, but MW4 Mercs is where MW4 really hit its stride and IMO rivals MW2 in its greatness. MW3 is a great game, but I don't recommend it because it's in that weird limbo where it's not old enough to run in DOSBox, but also not new enough to run on modern systems without significant effort, so unless you have legacy hardware sitting around for some reason it's probably not worth it.

3.) MegaMek - This is a free Java app that lets you play virtual tabletop BattleTech online or against bots, and has tools for building and modifying your own units to use in the game as well as tools for running narrative campaigns. I recommend Devalk's MegaMek video if this sounds at all interesting to you.

Finally, if you want to learn more about BattleTech lore, Black Pants Legion's Tex Talks BattleTech videos, Sven Van Der Plank and Big Red 40-TECH's channels, and Sarna.net's BattleTech Wiki are all fantastic resources. For tabletop BattleTech content I recommend the YouTube channels 4 Hands on Deck, Death From Above Wargaming, Trailblazer, and The Many Voices.