This is my first thread so please be gentle with me

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I have a
IG army but simply cannot fit the fluff for their home world into the Imperium so I decided that perhaps the best course of action is to make the world and it's people part of the Tau Empire.
First I'll give you an idea of the general background which I have changed slightly to fit that with the Tau.
The world in question was part of the Imperium but, as the centuries went by it lost contact with the rest of the empire. Over time the planet started improving and developing their own technology, heresy brought on from desperation as the world was constantly raided or invaded by Orks, all cries for help are ignored or go unheard. In the year 951M41 the system was attacked by a Ork Waaagh!, the largest invasion the population has ever faced in the worlds history. Once again calls are sent for aid but receive no answer.
For months the professional army desperately fought the Orks back but just when the military started to gain the upper hand several smaller Ork waaagh!s invaded the system. Victory now seemed impossible but aid finally came, aid in a form which they could not have ever possibly expected.
A Tau fleet, pursuing one of the smaller Ork forces that reinforced the initial Ork invasion, caught the Ork fleet by surprise destroying many before they could exit orbit. After many hours of skirmishes and significant losses the Tau fleet defeated the Orks. With no orbital cover the planets military gained the upper hand once again and, eventually destroyed the Orks that remained.
The world, now seemed to have been abandoned by the Imperium join the Tau Empire willingly.
The fluff isn't set in stone and to be honest the revised background is new.
Now I have a few questions which I hope you can help me with.
1: Would the Tau allow a newly integrated human world rule itself, effectively as a vassal state?
2: Would anything change for the people, would their culture and way of life change to fit the Tau standard?
3: The world wasn't settled by the Tau nor was it conquered, it is an entirely human world so would the Tau tear down human structures and replace it with Tau architecture?
4: As stated earlier the planet's population had improved on standard Imperial technology, ridding themselves of the AdMech before joining the Tau, what would the Tau's attitude be towards a human civilisation that develops it's own technology?
The forth point is really because I have a large
IG army and cannot be arsed to modify all of my guard into Gue'vesa. I also don't like the whole Imperial/tau mix look, any conversions I'll do will be subtle, for example the skull and wings on the cadian helmet is now the Ta'u symbol and wings, new sleeker looking las weapons and visored helms with integrated systems. I'd like to just use
IG tech so is it possible for that to occur?
5: The world has a professional armed force, not Gua'vesa in the traditional sense. How would the Tau view this and would the Tau use the planet's military formations outside of personal defence, i.e. defense of the Empire overall and perhaps aid in it's expansion?
6: The Tau's attitude to the world having it's own fleet?
That's all for now. Ultimately I'm kinda aiming for a Mass Effect feel where humans intermingle with aliens and I'm happy to accept anyone's personal views with regards to my questions or the planets backround if the established fluff doesn't answer them fully.
Automatically Appended Next Post: Moved to background section, Mods feel free to delete this thread.