Only problem is that the W54 is an old style fission weapon, while the weapon in this case is a star league (equivalent) technology pure fusion device. It's also about a quarter of the mass of the SADM based on the W54.
Eh, pure fusion devices need lasers and power sources. In the real-world, these lasers would be on the scale of NIF or various Z-pinch machines (i.e., the size of large buildings). Even in BT, combat lasers weigh at least half a ton (quarter-ton for the Clans) and are powered by engines weighing multiple tons, sometimes attached to magical "power amplifiers" weighing a fraction of a ton. Even with some imaginary one-shot BT capacitors, batteries, or other energy storage devices replacing engines and amplifiers, it's hard to see how any pure fusion device is made compact enough such that the system weighs a handful of kilograms. Honestly, it's hard to see how any pure fusion device weighs less than half a ton in BT. Even the Clans' small chemical laser with one shot of ammo weighs 516kg before adding the fusion material, reflectance material, and bomb structure.
BT lasers and fusion engines could probably easily produce lots of antimatter to act as triggers in pure fusion devices. But at that point, just skip fusion and throw antimatter.
There may be some way to use an explosively driven electromagnetic pulse or the gamma emission from a nuclear isomer to ignite fusion. Those techniques could be compact in theory, but so far that stuff is either rumored at best or been proven false so far. It's more in the realm of Eclipse Phase theoretical future physics than 1980s BT physics.
I think to go compact somewhat realistically, even in BT, you gotta go fissionable. But it's an imaginary universe, and lasers and associated power sources powerful enough to ignite fusion but small enough to be carried within a suitcase or grenade are ultimately up to the GM.
