The amount you lose when training at BW is considerably less than not training at all - studies show retention of size for months and months - and in a pinch I

The amount you lose when training at BW is considerably less than not training at all - studies show retention of size for months and months - and in a pinch I absolutely would go for a program that emphasizes bridges and planks and hanging. As for the rest - training goals can be multidimensional and this influences the optimal methods a lot. Training for martial arts, for example, tends to mean training for overall coordination and mobility, as well as strength and stamina. Judo players, MMA players, they can be strong, they can benefit from weights, but they aren't bodybuilders or powerlifters or strongman competitors. Eddie Hall, a strongman champion, has been covering his training for a boxing match on his YT channel, and while he does still do his presses and squats, he's slimmed down a ton. There is an argument around calisthenics having too many compound movements and gaps in difficulty progression, which makes it hard to overcome specific bottlenecks. But what calisthenics absolutely is great at is mobility and CNS engagement. Combine calisthenics with a yoga mat and doorframe bar with bands training to add more granular progression and isolations, and you have some really good overall coverage with minimum equipment. NB: One major reason we have historically seen more material about weights than bands is that it's easier to compare weight progression apples-to-apples. Bands change difficulty with slight changes in grip position, hence results are harder to compare.