Raylane It's good that alternative ways exist, but I don't feel that this is a viable option.
Bio5 costumes are about 5% drop chance, so let's say you get about 2 costumes/minute (about 40 kills/minute which I would consider quite fast). That's about 25 minutes for one costume box. However considering the time you need to storage, rebuff, and to make calculation easier, I'll just go with 30mins. That would be 2 boxes/h.
Now I'll take the popular example of Cast Stone (Garment) as it makes or breaks certain build. The box with highest odds is 0.37%, or 1 in 270. So on average you'd need to farm 135 hours to grind for that stone (by that method alone, which I admit will not be the case). However, due to the nature of that system there is of course no guarantee, maybe you get it instantly, maybe you will never get it in your whole time playing.
I think this issue mostly alleviates itself simply by more players entering the server now, so players who get lucky and don't need a specific enchant stone will likely just put them on the market.
But I can also see how it would be great to add a way to guarantee a specific enchant stone somehow (e.g. pity system).