Its more of I don't know a lot on Tau to where I'd feel comfortable playing one where I'm expected to know a lot past some fiery young new blood

Well to keep the plot flowing I think we'll have an Ethereal in an "advisory" position to monitor the progress of the Por'Ui in charge of the diplomatic mission. Would anyone like the position of Por'Ui? If someone wants Shas'Ui we can do that too. And those who wish to be "fiery young new blood" can definitely choose to be less experienced.

Might I humbly request certain Shas Ui by the name of Se'hen? If we do it that way?

Question will there be xenos mercenarys? If so Could we play a race of xenos that the tau will hire.
Becuse anytime I have joined a tau Rp they seem to have a curse of dying off early after I make a charcter. That and Tau names are pretty hard to rembere for me.

Depends on the backstory in question, but a Gue'vesa or Kroot is definitely possible

I might know of someone who would like the position of a Water Caste ambassador. Will have a definitive answer for you in the next few hours, hopefully.

what type of mercnearys will be allowed by tau? Possibly psykers? or possibly lone freebota or a Little known xeno race like those dog like ones?

Humans mainly, but even they wouldn't really be mercenaries per se, just auxiliaries to the main Tau armies in a manner similar to the Kroot or Vespid.

That would be awesome! I guess first one to claim that post gets it, and we already have a Shas'Ui, so the only leadership position at the moment would be a Por'Ui.

I've play the water caste before, I could do it again.

Have some info that might be helpful;
Tau Auxiliaries:
• Demiurg (space miners)
• Tarellians dog soldiers (reptilian)
- Galg mercenaries (frog-like)
• Hrenian light infantry
• Morralian deathsworn (Brutes)
- Ranghon (?)
• Nicassar (void-farers psyker)
- Ji'atrix (ethereal void-farers)
• Gue'vesa (human helpers)
- Formosians
• Brachyura (dexterous-limbed crustaceans)
- Scythians monk assassins
Those with circles have more lore and most likely to be on hand auxiliaries, those with lines are less likely but have cool stuff on them as well.

Now for some other ideas to just throw in their.
Fire Caste Cyborg (bionics)
Nulls/Blanks - probably not but want to get your opinions.
Air caste Assassins
Earth Caste tech support
Water Caste saboteur? Or would they make better assassins?

I lost it at Earth Caste Tech Support.