Just looking at what sponsorship animals are left.
I assume he's at around Otter as the material breath thing was mixed up with the squid's ink, right?
My thought, as far as giving each sponsorship animal something unique, is that some of them won't need something special, and I anticipate many of them will end up being somewhat redundant- for example, all the poisonous snakes just have different toxins, and share the method of delivery (I don't see spitting cobras, anyway.) And if nothing else, I don't see much of an issue with waiting a long time to get them all done right (I say this despite my favorite Harp Seal being near the end of the list, mind you.) Although I can't speak for Toady's work habits, if it were me I wouldn't mind playing with animal stuff on weekends, or every other weekend, or whatever, just as a pleasant change of pace. Obviously that last sentence assumes that Toady's main concern is that he doesn't want to delay stuff for the fandom too long, instead of just being sick of doing animals already.
Yeah, I pointed a bit ago that some creatures overlap with each other. Other animals may also overlap with existing features(like a snake's venom bite seems to be mostly in the game already). For some of the animals, Toady may get to them and realize there's an animal he really can't add anything new to. In fact, with probably a handful of these it will probably be a matter of typing up the RAWs and the research that goes into that.
Looking at echidnas, hedgehogs, and porcupines, they don't need a whole lot to be complete. Egg-laying is already in for Echidnas. the defense mode tag from armadillos can cover these guys. Together the biggest thing they need are their quills. For the most part, the quills will be a simple addition to the system already in place. The missing piece is the quills actually being able to do damage. As this feature would make for some interesting FBs I'm guessing it is going in. But looking at this there isn't a whole big chuck that needs done for these guys. And I can't think of anything that can be done for each individual to make a new tag for each.
The material breath thing seemed to suck up some time the way Toady makes it sound, but actually he probably saved time somewhere down the line by getting it set up now. Honestly, I am surprised at how people are already starting to talk like this is cutting into their fun. I mean, yeah it is harder to think of the creatures as features, but think of some of the stuff that is getting added to the game as a result. Every new tag is a new possibility for FBs isn't it? I mean, now the giant turtles from nowhere can go in to defense mode and maybe make it impossible to defeat it until it decides to start attacking again because it has an iron shell. New creatures with new tags means a lot more interesting stuff can happen and some of these new tags/features can open the way to other new stuff as well. The material breath bit sounds like it is going to add some interesting new possibilities to generated creatures.
The key thing to remember here is Toady will not always be working on new game mechanics, sometimes he will be adding flavor features like the animals. These kinds of things may not add anything to the backbone of the game, but they make the game a fuller richer experience. Honestly, he needs to do it to keep the game interesting. Think about it, the new towns are interesting and awesome, but the new crypts/dungeons/sewers and the new animals/night creatures will make this update Fun.