First of all the option only exists in Lobby because the Rules state it must be declared at the start of the game. Perhaps an Option to use MODE anytime would be OK.
I don't know what the Devs call the Window but when right clicking player name in Lobby you get to "Configure" (the window with Mines, etc) Add Two Check Boxes... Use Rapid Fire for Mechs and Use Rapid fire for Vees, etc. Selecting these boxes goes through each unit in Player Force and turns on any Use Rapid Fire option (Note some units have more than 1 MG so it has to check ALL of them)
This doesn't clutter the GUI, places the commands appropriately to the Player and would allow the Player to keep the option off for Bots who shouldn't use the option on Mechs.
So you want a FASTER way to turn on rapid fire MGs? As it stands you can go over each unit and turn on RF. If you haven't seen it.. Right click your unit -> configure - > equipment. You can also turn on hot-loading LRM ammo.
Yes, a faster way please. It gets very cumbersome and error prone when the unit list starts hitting 30+ items.
Thats what I thought. The option for all vees I do like. Not sure for mechs since it causes additional heat buildup.
This has been implemented in the GitHub repo: https://github.com/MegaMek/megamek/commit/04ac57cb6c15101efbca8fa5c23709ffd42c4c40