i think if lego were to remold animals, they should do it right from the grounds up. this means having exchangable bodies and exchangable heads. after all, lego is all about building and not so much one-piecey.
imagine if you can swap out the horse's head and make a centaur with a minifigure's head, for e.g. or mix a lion's head with bear's body, give it a pair of wings and a serpent's tail and you get a chimera. or mix an oversized eagle's head with a horse's body and a pair of wings and you get a gryphon.
there won't be so much asking of let's make so-and-so...and instead the action will be left to the fans.
the way to make this work is to make the body parts swappable.
as for specific animals - i'm mostly for larger mountable mammals mainly to be used in fantasy medieval settings. as such, i would like the:
1. bear (swappable version and with proper slot for a rider - not the current one)
3. giant wolf (or dire wolf)
4. wild boar (giant version)
5. tiger (or giant cats - recolor for cheetah, puma, jaguar).
6. giant eagle
9. dragon (rehash of the smaller dragon from the fright knights, not the 06/07 versions).
another plus, is the versatility of having animal body parts to be used as deco pieces. e.g. the head pieces can be built as trophies to be mounted on walls. stick the head piece on a round shield or a 2x2 plate and use it as a wall trophy.