But then is it really a Hezrou? Why not just use a different demon or make one up completely at that point. It doesn't seem like you are embracing the Hezrou, but instead designing it into something completely different.
Is there anything about the hezrou's lore or stats that says it must look like a frog? I see art, stats, and lore as all mutually reinforcing. The hezrou is not amphibious nor does it have any association with water, there is nothing distinctively frog-like about its behavior, and none of its mechanics indicate it would be a frog – it could just as easily be a skunk or an owl or a jackrabbit based design.
I am looking deeply into its identity over the whole span of D&D. And I realized that a lot has been lost. The problem there is that those distinctive things which have been lost helped to somewhat buoy against the "generic frog monster" issue where you have a bunch of monsters competing for "frog monster" – hydroloths, banderhobs, bullywugs, froghemoths, grung.
I do agree it's important to honor a monster's origins/roots, but sometimes that also involves looking harder at what's not working, and then finding creative ways to adhere more closely to its origins/roots (or implied origins/roots) in order to make it more interesting at the game table.
No one in particular is jumping out at me, but I like parts of several. Also, just to be up-front: I hate giving demons masks (seems more of a devil thing to me) and I trend to more "traditional" demon designs.
With those caveats: I Iike the general design of D without the cyborg bits + the back and ears of B + the feet of C. Does that make sense.
Yes, totally, much more of a classic fiend look. Thank you for your feedback!