I think it would be comfortable to have a single topic dedicated to the discussion of Tau favours, so we can brainstorm about them without mixing it with other aspects of the Tau fleet.
First thing that comes to mind is: in what aspects of the Tau lore would they be best based on? Two of them have been talked about:
1) Tau Castes
2) Tau Septs (planets)
Of those 2, I believe number 2, the Septs, are the most appropiate for favour design. The reason behind this is that all other factions use "subfactions" as a basis for their favours: Imperial organizations, Chaos gods, Ork Klans, Eldar Craftworlds, and probably Space Marine Chapters. All of them are subfactions in the sense one would paint their TT fleet or ground army under their colors, and be coherent as a force of said faction, coming from said subfactions. The Tau equivalent of this are the Septs, so for me they seem like the most lore-friendly choice by a wide margin (and have defined, stablished color schemes!). In contrast, Tau castes would not be well represented on a Kor'Or'Vesh fleet: all Tau spaceship crew are from the Air Caste -as it is literally their role on the Tau society- as well as Fire Caste, maybe with a single Ethereal on board, some Earth Caste engineers, and depending on the mission, some Water Caste diplomats. There simply are no Tau ships with crews completely composed of members of the same caste. Simply put, Castes are not subfactions. An Space Marine equivalent would be to give them the favours if the Techmarine, the Apothecary, the Chaplain and the Librarian: it would make no sense at all. Same goes for the Tau Castes.
The following is a list of some Sept overviews quoted from Lexicanum (http://wh40k.lexicanum.com/wiki/Tau_Sept). Following said page, I'm dividing them into Expansion Spheres.
- T'au, homeworld of the Tau. Capital and spiritual, political, cultural, and administrative centre of the Tau empire. Its citizens are considered especially learned and wise.
- Pech, homeworld of the Kroot.
- Vespid, homeworld of the Vespid.
- Tau'n, first offworld colony, Tau from this world are considered to be pioneers.
- D'yanoi, having been isolated for a time from the empire, its inhabitants are considered somewhat rustic and backwards.
- Bork'an, centre of learning and academia.
- Dal'yth, cosmopolitan and trader-friendly.
- Fal'shia, centre of technological development, Tau from here are considered great problem solvers.
- Vior'la, a major military centre of the empire, its Fire warriors are considered especially aggressive and skilled.
- Sa'cea, another military centre, this sept has a very high proportion of very disciplined and honourable Fire Warriors.
- Au'taal, a beautiful sept, whose citizens are considered easygoing and often lazy.
- N'dras was abandoned for unclear reasons. Its remaining inhabitants are regarded as unstrustworthy, quick-tempered, and of brooding countance.
- Ke'lshan has suffered several raids by several alien races. Tau from this sept have grown mistrustful, solemn, taciturn, unfriendly and sometimes openly hostile to alien races. Ke'lshan was invaded by Hive Fleet Gorgon and played an essential role in stopping it.
- Elsy'eir is known for its poetry and artwork. Its citizens are considered intellectuals and well-respected for their creativeness.
- Tash'var was raided several times by Orks and pirates. Its people are regarded as tenacious, hardy, practical and courageous.
- Vash'ya seems to be primarly inhabited by members of the Air caste.
- T'olku is known for the skill of its Ethereal diplomats.
- Ksi'm'yen's colonists seem to be associated with luck, subtlety and opportunistic subterfuge.
- Fi'rios whose pioneers are recognised for a tenacious refusal to accept defeat, tempered by a stoic acceptance of the price all must pay in the furtherance of the Greater Good.
- Mu'gulath Bay, previously known as the Imperial Hive World of Agrellan. (Destroyed)
- Vas'talos, previously known as the Imperial Fortress World of Prefectia.
By clicking on the link posted above the list, you can click on their names and investigate their histories if you want.
The following is just a quick list of possible favours I wrote for the Tau Implementation Thread (viewtopic.php?f=3&t=1564). They're the product of a quick brainstorm, so please feel free to improve them, change them, or ignore them completely. In fact, I'll probably post here later with a different list, once I've familiarized myself enough with the Septs.
Necroledo wrote:- T'au: boosts morale of this ship and nearby ones (reduces chance to Insubordinate).
Ability: boosts the crew value for a short time, representing the Tau showing their best to the proud defense of their homeworld.
- Tau'n: allows to bring a free escort from the military fleet; for example, the Castellan.
Ability: project a big frontal, flat shield that blocks projectiles, ordinance, boarding actions and ships for a short time.
- Dal'yth: allows to bring a free escort from the civilian fleet; for example, the Messenger (because of tracking systems). Ship gains tracking systems itself.
- Bork'an/Fal'shia: increased precision and range for all weapons.
Ability: greatly increases rate of fire and ordinance reload speed for a short duration. Inspired by the Riptide battlesuit.
- Vior'la: increased troop value. Allows the ship to perform Lightning Strikes.
(something needs to be done about Tau and Data Missions...)
- Vash'ya: increased turret numbers. If the ship is not moving, it gains extra shield strength. Inspired by the defense platforms of this planet.
(maybe it would be interesting to have a Farsight Enclaves favour too...)
At least, I hope it serves as inspiration for brainstorming. Now it's your turn!
EDIT: now that I think of it, T'au would probably work much better as the vanilla subfaction (ships without favours). One Sept has to bring the vanilla color scheme