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Have you tried to use the (G3)BG2Tweakpack and its 'Change Avatar When Wearing Robes or Armor (Galactygon)' -component, which makes every character that has no armor or leather to use the hooded animation/avatar? It's part of the Cosmetic changes and it installs with BGTutu and BGII too. The only downside is that it uses the hooded avatar for Kensais etc. too as they can't use armors...
Sorry, but that's not exactely how the component works - it works as thus instead:
The
G3 Change Avatar component allows a dual-or muliclass character (such as a thief/mage) to look like a mage when he's wearing robes, but to look like a thief when he's wearing leather armor.
However as pure-class mages and sorcerers can't wear leather armor in the first place, they cannot equip it and thus not look like a thief wearing leather armor.
Besides, the "thief wearing leather armor" avatar is different from the "mage with hood" avatar introduced by the
BGT Tweakmod.

@ Ascension64: Thanks a lot, that managed to do the trick. I was indeed wondering if it were possible to remove a line of code which made the component "check" whether or not
BGT was installed, and that was indeed the one. This time it did not skip it during installation, but asked me if I wanted to install it, which I did, and it works now despite me using EasyTutu

THANKS!