Sorry, I didn't read everything, so I don't know if somebody said that but here 2 ideas :
- Elfangor thought morphing and demorphing must be too long and the Yeerks would arrive and torture him (or maybe make him a Controller, but I think more about a long, very very long torture by Esplin); morphing only and leave with the Animorphs make them in danger because he mustn't have so many morph, maybe only kafit or that kind of things, and Yeerk could find him out easily, and maybe find the Animorphs too...
well, not very good explanation but... this one is better:
- When the Ellimist give him back his body, he didn't give him back the morphing power nor the capacity to acquire it again, so he couldn't morph any more! even if he has the morphing cube, he couldn't use it...
this last repear the KASU
don't you think?