Catalyst Game Labs released their A Time of War companion book as a .pdf you can get to expand your Battletech experience.
From the announcement:
Launch yourself into the universe of BattleTech with new technologies and prove your heroism to House Lords and Khans alike! Visit strange and distant worlds, and battle alien beasts beyond your wildest dreams! Demonstrate new combat techniques both in and out of the cockpit while navigating the intricate layers of neo-feudal politics! Whether your are a House regular, a pirate smuggler, a noble scion, a deep space explorer, or just a thrill-seeking adventurer, bring your experience to a whole new level!
A Time of War Companion introduces advanced rules for BattleTech role-players and gamemasters alike. This core book expansion showcases advanced gameplay options including Advanced Tier martial arts, “heromode” gameplay, metaskills, Trait Checks, and more! Use character design templates to quickly generate new characters and NPCs, or even convert older characters from previous MechWarrior rule sets! Gamemasters, use the world-building rules to bring your players to exotic new locations, introduce them to equally exotic fauna you have created to greet them there, and give them the chance to fight for—or against—a host of new technologies rarely seen in the field! The tools to enhance your role-playing campaigns are here for the taking!