personally, i like the RPG-esque vibe that these guys carry, and in my opinion, there is room for some elements borne from the rpg style. that blather aside, i like the concept of having a beefed up challenge added to the game, thinking about all of the bosses that we've seen over the years, all of the different play styles and strategies that have been created and how the game has been evolving around these things, having a unique "boss" team like this would really force us to push ourselves to our limits to keep up and come out as the victor.
with THAT said, i'm sure if for sake of argument, if this was ever implemented, the devs would most likely revamp the designs for a more terrarian feel, but even as a "beta" concept, they have a very cool look about them, in which i know i can certainly appreciate.
i even found it intriguing that you had even given ideas for the the AI they would have. sure, they would give us an idea on what they would do, but once you put it into motion and see it in actual play, it would prove to be "swamping" very quickly. i mean c'mon, look at duke fishron and all of his shenanigans!! but with some careful planning and patience, it is a very realistic goal to be able to stand up and beat them....after many many bloody deaths and practice!
in conclusion to my analysis, i most definitely support your idea
CHEERS!