In my games I set the following limitations for characters, mind you this is for a 5000 XP build and aiming for Mechwarriors/Pilots fresh out of training. First limit I impose is no Stage 4 modules, pretty no brainer. My second limit is on Gunnery and Piloting skills, I impose a limit of 4 Gunnery and 3 Piloting. These skill limits on Gunnery and Piloting produce a baseline in classic tabletop skills of Gunnery 3 for a Clan character, and Gunnery 4 for an Inner Sphere character. On the Piloting side this limit produces a Clan skill of 4, and an Inner Sphere skill of 5.