I was thinking something
Some /a/nons said that the reason why Angel didn't regenerate his arms after losing them was because he wanted to die, but I don't think it has sense at all. I mean, yeah, it's true, at first he wanted that, but after Aki saved him he never thought or said something about dying. He knew that Aki would feel bad if he died due to his trauma, Angel also kinda wanted protect Aki and cared a lot for him. Why would he wish to die now?
I've thought if there is any reason behind this, maybe something we don't know about Angel yet. Otherwise it's character regression or maybe Fujimoto was just being a hack because I don't get how Kobeni got her both arms.