Independant Forts question
 

Is there a way to have it so that an independant province with a fort in it will have its garrison fight an invader instead of going into a seige when attacked?

Re: Independant Forts question
 

Yes. It involves a specific sequence of commands.
Here is one from my Poke-in-the-Eye chaos map.
<font class="small">Code:</font><hr /><pre>
#setland 45
#fort 2
#knownfeature 615
#defence 31
#commander 1107
#randomequip 4
#bodyguards 8 1106
#units 5 1105
#owner 23
#nostart 45
#commander 1447
#randomequip 4
#bodyguards 7 1444
#units 9 1442
#commander 774
#randomequip 4
#bodyguards 6 773
#units 11 773
</pre><hr />

Set the land, place the fort, put units there. THEN assign ownership and then put more units.
Courtesy of Endoperez for finding this for us

Re: Independant Forts question
 

Thank you both. No risk of the guys chosen to be inside starving to death?

Re: Independant Forts question
 

They will starve. You'll have to give the insiders supply items (endless wine skin, cauldron of broth, summer sword, nature mages), or sites with supply bonus.

The trick is, essentially, that you can set units from different nations to start in the same province. Usually they fight on the first turn, but if there's a fort one side starts besieging the other. The fort will never be stormed, though, and there are independents and "special independents" who share the white flag.