Insects' life cycle
All in all the idea is not too bad, although I prefer to believe that too many bugs are overwhelming, moreso for the new players jumping into the Backyard. Sure: on paper it sounds good, but imagine all those mobs in the game. You would have ladybugs in 4 forms, aswell as other insects too. The Spiderlings are already in the game so there's no need for it? I dont think the bugs should "evolve" but rather "respawn".
"Relationships"
Now. This idea is way better structured. I do think that those "relationships" between the bugs, you are talking about, would actually be good for the game. The insects already have a daily routine: They sleep, they hunt in order to eat and they just do their things At the moment there is no true "bond" between ants and aphids or "rivalry" between ladybugs and ants (except the times ants attack a ladybug by mistake). Would also love to see Wolf Spiders actually kill smaller insects, or even Orbweavers, since in reality they don't "work" together.
Taming
On this topic all I have to say is: there's no need to have a pet that fights for you. As far as the combat goes, in my opinion it is ok where it is at now. In fact on "Whoa!" difficulty, if you don't manage to perfectly block a wolf spider's attack, any of their attacks, you will pretty much die, even if you spam Smoothies and Bandages. But if you DO perfectly block it, you're good to go!
As far as I know, the Devs will be introducing a taming system, in which you can tame aphids. It would be cool if every now and then they would drop an aphid honeydew for you. On the other side:I don't think it would be beneficial to the overall experience having ladybugs protect you or ants do your heavy work and carrying fiber/meat or wahtever. I hope you get my point.
My humble opinion
In my opinion, some of the suggestions you made are great, such as the Relationships one. And no, I don't think it is "too late", since most of the AI still needs some attention to detail and some serious work on pathing and patrolling in general. The bugs in the backyard now are buggy, no pun intended. But it's ok because this is Early Access and we're here to give feedback.