This would likely be less damaging if the bomb could be largely based on H-11B fusion rather than DT or DD fusion. The latter inevitably produce large numbers of neutrons.

At gigaton scales, thermonuclear devices become easier to build in a sense, because the assembly has more time to react as it expands. More stages are needed to compress that very large final stage, though.

The argument reminds me of Freeman Dyson's H bomb propelled interstellar concept, which exploited the fact that per unit of energy output, deuterium was (at the time of publication, in 1968) thousands of times cheaper than fossil fuels.