Bitter Iron > Bitter Duty > Praevian interaction?

[Yodhrin]

A Consul Praevian in a Bitter Iron RoW, being an Independent Character, has the right to take the Bitter Duty special rule if you so choose(gaining Hatred: Traitors), however how does it work in practice?

Bitter Duty states that "A unit that includes any models with this special rule may not be joined by any model that does not also have this special rule.", while the Legio Cybernetica rule states "An army that includes a model with this special rule may select a single [unit of robots] as part of the same Force Organisation choice...etc", and the Master of Automata rule states that "A model with this special rule may join a unit that includes one or more models with the Automata Unit Type...etc".

My initial reading was that the Praevian *could* take Bitter Duty, but if he did he wouldn't be allowed to form a unit with the Cybernetica he takes as part of his FoC slot, however it's been pointed out to me that Bitter Duty technically prohibits models *without* Bitter Duty from joining units with it, not models with it from joining units without it, and per Master of Automata it would be the latter situation here, so is the strictly RAW reading instead that he can take Bitter Duty and can join the unit of Automata, but only the Praevian benefits from the Hatred: Traitors so granted to him by the RoW?

That reading does seem a bit against the seeming Intent of "Bitter Duty only with Bitter Duty", but I would be comfortable with it anyway since it's for thematic consistency more than any huge rules advantage.

[GodEmperorOfMankind]

By that same thinking you could join an IC with bitter duty to an IC that doesn't have it, which to me is definitely against the intent. 

However in this specific case of automata I personally would allow it, as the blurb at the start states the intent of bitter duty, and unthinking automata would not care for the weapons or tactics used, and do as theyre told by the praevian. 

I would suggest clearing it with your opponent first, and explain the above. 

Units other than automata I would say a hard no.