I realized you might have come up with this list after looking around on the wiki already but the hydra, cerberus, phoenix, archangel and queen bee have all had someone try their hand at creating such a monster within the past few weeks.
From your list, I'm most interested in the hydra and pegasus.
I'd also like to see another lighting element monster, the raiju and thunderbird are ok, but something like a lightning elemental would be nice