I very much agree with you that the inferior function is tricky. But don't totally write off the possibility that you could find a Ti logic to using your Fe, as soon as you are aware of your Fe. Actually, many consider the inferior function to be an aspirational function, so that it is actually something which you admire in others. But, not everyone likes babies, so YMMV. For me the reason to actively try to develop my inferior function is that I know that it would make me a more balanced person. Don't you think there could be expressions of Fe that you would think would make you a more well-rounded person?
I don't think that it happens very often that any function becomes more developed than the dominant, but at least in theory it should be possible, since the MBTI type only signifies preference among functions, not abilities or talent. In some circumstances it seems obvious to me that the tertiary can be more developed than the auxiliary for instance.
The tertiary, being of the same attitude as the dominant (introvert or extravert) will have the support of the dominant in its attitude, and if the context heavily favours introversion or extraversion, it seems to me reasonable that the auxiliary will be comparatively less developed. Of course the inferior doesn't have the same relation to the dominant, so that's a different issue.
I think you are right in one sense though, namely that it takes time for the use of any function to develop, which explains why normally the tertiary doesn't develop much until in your 20s and the inferior until your 40s. But that is a generalization which isn't valid for every single individual. There is, as I understand it, nothing intrinsic in the MBTI system that rules out exceptions in this case.
As for the parallell development of dominant and auxiliary, I agree that it would make a person more well balanced to have equally strong dominant and auxiliary. But not everyone does... An introvert with a weakly developed auxiliary will be very shy, so it's not healthy, but still possible. Again, maybe this was your point as well...
Coming back to my point about contexts again, what I was thinking of was the fact that perceiving and judging functions as well as introverted and extraverted functions do different things. As an example with the tertiary, it is in my case Ti, which I can use for judging as opposed to my dominant Ni which is a percieving function. In your example of Fe vs. Ti, both are judging, and admittedly Fe will not get much attention unless your Ti lets it, but since Ti's and Fe's strenghts are different, in some situations (think social interaction) that could be preferable even if your Fe is less developed than your Ti.
But obviously it would be a scary thing and require you to recognize your true self as not being identical with your dominant in order to acknowledge your inferior and give it space to function.
And if I still don't make sense, ask again.... As I said, I'm not that into this either yet... I just like to try to make sense of it.