The enemies that I want to see implemented in ZC in the future are enemies that are seen in ZQuest, but were never implemented. Here's what some of them are: These are all from the new enemy tiles.pdf file that came with ZC for four years now.
* Fire/King Dodongo (breathes fire)
* ALttP Moldorm
* Level 2 Batrobe
* The Aquamentus' - It would be great to see the BS Aquamentus from Level 7 in the original BS Zelda for the first time
* Ceiling Masters and Floor Masters
These are the "newer" monsters that never were implemented, but it still would be nice to see these in action for the first time.