I really loved the A-story in "The Begotten". Odo dealing with "daddy issues" while becoming a father figure himself. Obviously some parallels to the episode back when Odo raised a Jem'Hadar.
I felt that Mora was a well-developed and interesting character. And James Sloyan is a great actor. I wish we had gotten to see even more of him (like the original plot of "Extreme Measures" before it was re-written).
Odo's back as shape-shifter! And all he had to do to get there was "eat" a baby. Certain Odo regrets that some. Wonder what the Founders think of it?
I loved seeing Odo smile. This fatherhood thing was one of the few thing (other than Kira) that really gives him joy. And that's cool to see. Too bad Kira was busy, or she and Odo could have shared the moment a little more and been like a little family.
Speaking of Kira's story, the Bajoran way of giving birth seems a little weird. Shouldn't birth be something that just happens when it's time? Not that you have to be calm to do so. Wouldn't that mean that a pregnant Bajoran woman that are in stressful situations (like being imprisoned in an Occupation) would never be able to give birth? Seems a little weird. I give them props for trying to make alien birth different, but the way they did it seemed a little illogical to me. But, hey, at least the kid isn't born from the back like the Ocampa in Star Trek: Voyager.
So, since we know that Bashir has been replaced by a Founder by this point that means that the undercover Bashir Changeling (UBC). helped give birth to the O'Brien kid when Kira was in labor.
And it let a baby changeling die on the station versus saving him. (You have to think that Founder medical science for their own kind is better than what Mora Pol and a humanoid Odo could provide.)
Certainly UBC would have used ALL his knowledge of changelings to try and save the baby alongside Odo and Mora Pol, and not just the "limited" knowledge that the real Bashir would have had in that situation. (UBC would have just kept it a secret what he was doing.) Remember how frustrated Odo was that he couldn't just link with the baby and "talk" to him? Well UBC could have done that. And, I think, certainly did. Maybe that's the real reason the baby changeling learned how to shape-shift so much faster than Odo. It had nothing to do with Odo or Mora's teaching methods.
And even with all UBC's [likely] detailed knowledge and skills with dealing with sick changelings, the changeling baby died anyway. Sad. But it also merged with Odo somehow and turned him back into a shape shifter. Seems pretty lucky, doesn't it, that that dying baby changeling had exactly what Odo needed in order to overcome whatever changes the Founders had done to him that made him a solid? Well, maybe it wasn't as lucky as we think. Maybe UBC did something to MAKE it that way. That would, of course, imply that at least one Founder (and by extension probably all of them) were OK with Odo becoming a shape shifter again. So much so that they went out of their way to make it happen. Hey, maybe the Founders thought he'd had enough punishment. Or maybe it was just this one undercover Founder, who had to see the humanoid Odo suffer through back pains and the like (because he was acting as Doctor Bashir), and felt sorry for him enough to intervene.
Here's yet another idea about the baby changeling in "The Begotten": maybe there was no baby changeling at all. Perhaps older, more mature changelings, like UBC, are able to separate part of their body and still be able to control it. (Yeah, that would pretty much invalidate the "blood test", which are probably useless anyway.) So maybe that "baby changeling" was just part of UBC, who sent it to test Odo, or to allow him to turn back into a changeling or whatever.