Honestly a middle ground is the best idea. Mech raids are only allowed if a certain amount of MTF are on, and if the CI are outnumbered by MTF then the CI has to try harder and play better than the MTF. Honestly the middle ground is the better idea because it would allow people to use more strategy instead of blindly running into combat. Keep in mind MTF get a free Mech-like support SCP if enough CI are on that they can use against CI, much like CI can use a mech against the MTF.