Just about any secondary would work with Thugs, at least with a minor bit of “technological” hand waving. Some are stronger than others.
Storm? Massive damage. Thinking Sean Connery in the Avengers movie with a portable weather control device. Same sort of explanation with Sonic, thermal, Time, FF, Cold, Radiation, or Nature. Traps or TA? Clear tool base. Dark could be tricky, but explaining the secondary as originating from an ancient cursed totem... it could work. And let’s be real, an “ancient cursed totem” can provide a story for just about any secondary once that narrative door is opened. Hell, Family Consigliere's seem to mix super strength and gravity domination. Basically, any of this depends on the background in which you’re willing to invest.
As for the suggestion above that MMS are as expensive as dominators, that hasn’t been my experience. Investment in the unique pet IOs IS very helpful: 10% def to all, 20% AOE (25% at level 50), and 30% resistance (35 at level 50) is a significant benefit. But depending on the secondary and its needs, there is a lot more flexibility with Thugs than some other primaries (mainly due to Gang War and the ability to slot the aforementioned pet unique IOs / all six can get dumped in there if you want). For example, the 2 +def uniques, along with maneuvers from the mastermind will give you defense capped pets on IOs, when you factor in the Enforcers’ maneuvers ability, with FF, Cold, or Time.
Assuming you start on standard difficulty, there are certain levels in the 20s at which it becomes fairly easy to increase the challenge: level 22 (worthwhile slotting of crafted IOs), Level 24 (gain 2d tier 2 pet), level 26 (gain tier 3 pet), and 32 (second upgrade power).