hi,
i dont know wether this will help but there is already chapter apporved rules for Gue'vesa
http://www.eastern-empire.com/downloads/guevesa.pdf, may advise use these rules so that way
GW cant argue that its not "
GW written" and you can use it in stores.
However if you are dead set about using homebrew rules, probably use the same points as guardsmen (5 points?) with the sergeant being an upgrade/promotion to a regular member (like in tau Dex) at +10pts with +1
LD and the option to take wargear a markerlight or drone controller for free and pay for drones, also up to 3 models may swap lasguns for: pulse carbines 5pts, pulse rifles 10pts , squad may take emp grenades at 5point per model.
i think Gue 'vesa are at the bottom of tau society so giving them all the best tau wepaons would seem a bit wrong so up to 3 is justified and act as special weapons. carapace armour upgrade at 5 Points per model may be quite good to show possibly "elite" gue vesa who have worked they way up in the tau society to be allowed to take better equipment. sergeant should be armed with pulse pistol, close combat weapon with ability to swap one or other for pulse rifle or carbine 10/5pts.
you could go and allow one model to be armed with a heavy weapon: flamer 5pts, burst cannon 10pts, plasma rifle 15pts, missile pod 15pts, fusiongun 10pts, railrifle 25pts? but this may be me going out of control i just love the idea of gue'vesa and for me the more options the better