most IS Mechs are, by default, omni-mechs . . but not as sophisticated as the clans.
weapon-slots have allways been there with IS-Mechs, but they are not modular.
every weapon that is built into a certain slot gets hardwired into the system.
that makes it HARDER to switch out the weapons, true, but not impossible . .
there's IS Mechs with more than half a dozend configurations and it's still the same mech.
don't tell me that's not omni-tech right there. if it were impossible to switch out weapons,
it would be impossible to do maintenance in the field, if there's not exactly the same stuff
available to replace destroyed components.