>>18584985The monster fusing only really worked on the PSX because it was low poly with low-res textures so all monsters had corresponding polys for each body part, and all their textures could be mapped the same way without it being to noticeably ugly.
For some monsters, some limbs were flagged as 'invisible' - like wings on most terrestrial monsters, forearms/legs for birds/serpents and/or tails for some humanoids. you'll notice that if you say fuse the snake monster and a bug you end up with a snake with bug legs and wings just appearing where there weren't any.
And well, it worked well on the PSX but would have been more noticably ugly on the PS2 with obvious texture stretching and it did cause somewhat limited monster designs though they did have a surprisingly awesome variety to begin with.
TLDR; JC1 fusion worked because of the PSX's limited specs. It would have been an ugly mess on the PS2