I made a python script that will recursively walk through all directories and look for .../Chassis/ folders. When it finds one it goes through each .json file and checks if it has fields Max Tonnage and Initial Tonnage, if it doesn't find those fields it skips to the next. Then it subtracts a third of the max tonnage from the initial tonnage - letting you add an additional 30% of gear!

You can use this in vanilla by dragging the script into your \BATTLETECH\BattleTech_Data\StreamingAssets\data\ folder and executing from the command line. If you are playing with mods, drag it to your \BATTLETECH\Mods folder and execute from command line. I ran this while running a ton of additional mech mods and it threw no immediate errors, but it hasn't been extensively tested. Use at your own risk.

If anyone knows how to convert a python script into an .exe, please let me know. I gave py2exe a shot and couldn't get it to work.

To use:
Drag into Mods folder open up command line, and then click and drag the script from the folder into the command line window and hit enter. Boom. Then move it over to your StreamingAssets\data\ folder and do the same thing to reduce the weight of the vanilla mechs.

If 30% is to cheaty for you, open the script in note pad and look for:
newTonnage = iTonnage - (tonnage*.3)

and change .3 to whatever you are comfortable with.