So as always when bored in work I start thinking RPG.

Does the NDS system have any playable animal races in the vein of Blue Roses Rhydan? Maybe stolen from Star Wars?

how easy do you think it would be to do?

Dunno about Rhydan (or Blue Rose) but..

Realms of Terrinoth has Catfolk (and Half-Catfolk). The Core Rulebook also has a fair few examples to work with.

Making animal people is as easy as taking an archetype and replacing its special abilities with appropriately animalistic ones (such as natural weapons, and enhanced senses).

Rhydan aren't furries; they're straight-up sapient animals. Blue Rose lets you play as a telepathic horse if you want to. This may make things somewhat more difficult.