So if you are staying true to fluff, Panzer is partially correct when it comes to FSE. They have access to most standard T'au Empire forces; however, the emphasis on fighting style is very different. FSE will rarely employ static gunlines. They favor mobility. Proper use of FSE should feel like a dance with the battle lines ebbing and flowing with your will.
Crisis suits will almost always fill a critical role in any FSE strategy (maybe only a small contingent but almost always present). If you are taking infantry units, they should probably be mounted (CDR Farsight learned his lessons about infantry on foot on Arkunasha). This is not to say they can't employ gunline tactics when necessary, but they like to retain the ability to pick up and relocate quickly.
Riptides are actually pretty freaking rare in the FSE, and I personally don't remember any canonical references to Ghostkeels, Tidewalls, Stormsurges (this could be due to all of the lore being relatively old and the new stuff being extremely lazy), but FSE do receive clandestine resupplies from time to time from the Empire, so theoretically they could have limited numbers of new stuff. Experimental stuff (I.E. Forgeworld) probably wont have a place in a FSE army unless you reason that they came with a resupply or FSE Earth Caste reverse engineered designs. They do have some indigenous standard and experimental production and development in the FSE.
If you are pursuing FSE in the first place, I'm sure you know Ethereals (with the exception of Aun'Shi) are out of the question.
Oddly enough, the Enclaves seem to have less integration with auxiliary races even though their particular brand of Greater Good could be argued to be more open to inclusion. Perhaps this is because the Ethereals sometimes use unnatural means to get auxiliary races to comply and assists (Vespid helmets), and Farsight himself doesn't think it's right to push their beliefs on anyone who doesn't want it. Modeling vespids with predator heads would actually be a really cool conversion to represent Vespids joining the FSE under their own free will and not the influence of the ethereals.
All of that being said....if you can come up with a compelling reason why your FSE list is the way it is, then I'll fight alongside you wearing red any day!