SSWMs are also good for Active Probes and Improved Sensors, which, like TAG, a point or squad only needs one of to get the effect.
I’ve also used them for ECM Suites, but I think that’s me house ruling, and not supported by official errata.
The new Callisto Clan Medium BA sorta shows what SSWMs can do to mount large weapons, specifically an ER Medium Laser, LRR, or SRM-4. But with the possible exception of the ER Medium’s range and damage concentration, it’s pretty underwhelming compared to the five SRM-2s carried by a standard point of Elemental suits. You’re probably off designing around, say, a Spheroid Standard Medium Laser on each suit or using DWPs if you want heavy, concentrated firepower.