A few more questions...

pg 7, it says "When a model suffers an unsaved wound roll a d6 and consult the table below"
how does this work with multiple wound models? Do you roll on the table every time they suffer a wound, or only when they lose their last wound? The latter is how I assume it should work, as otherwise what would be the point of taking multiple wound models if they can be put out of action with one shot, but it is unclear...

pg 12, "Heroes have the Skilled Rider and Move Through Cover special rules." should also include "Skilled Flyer," which is exactly the same but applies more appropriately to jump packs...

Markerlights: First, Markerlightrs are not even included in the armoury. This is odd in that the ML is the primary weapon of the Sniper Spotter, and all Pathfinders carry one mounted on their Pulse Carbine. Also, in the codex the leaders of Fire warrior and Stealth teams have the option to buy Markerlights for 10 pts (50 cred)... was this omission on purpose or by accident...?
Second, in the Tau Empire codex, successful Markerlight hits can be used by certain subsequently firing friendly units or independant characters for a variety of purposes, from augmenting Bs, to reducing cover saves, to lowering leadership for pinning checks...
Since you explicitly state that
"Despite moving together, models are never considered to be a “unit” for any other purposes." on pg 5, does this mean that ML hits can only ever be used by single models? Or, is it possible for models who move in coherency as a group to use a single ML hit as if they were a unit?

Drones and Drone Controllers: as above, since models are never considered to be a unit, do drones that are taken by a hero via a drone controller still have to remain within 2" of their controller? And does this affect their unit type, which in the codex is specified as "same as controller"?

And why can't Gretchin gain experience? This seems odd, since they are hardly savage beasts... if I remember correctly, Rebel Grotz in GorkaMorka could gain experience in the same way as orks...

Also, some errors I think I've noticed...

pg 9, under the heading Special Weapons, you refer to Tau Plasma Rifles when I think you mean Tau Pulse Rifles/Carbines and Pistols...

Also, Tau Rail Rifles are not noted as Spcl or Hvy in the weapons list when they clearly should be going by the rules for SW on pg 9.

Thanks for the clarifications Nate!

And go right ahead an use any of my ideas for a kroot mercs list, I'll start a new thread on that topic to keep things separate, and update it as I can with ideas for the list, points values, wargear etc.
And I heartily agree about the Genestealer Cult list. My friend and I are getting pretty excited about skirmish 40k, and he's a nid player so we've already tossed around a few ideas for Stealers cults as well. I'll post any ideas we come up with on that as well.

Also, I forgot to specify the main reason I asked about the controlled drones... if they are considered to be the same unit type as the controller, does this mean that the hero confers their move through cover and skilled flyer rule over onto the drone? I think that it should, since if the hero dies the drone dies as well, and since it would be kind of silly for the drone to have to remain in coherency and not gain the movement bonuses (as the hero will definitely be spending lots of time hopping around in difficult terrain to gain a cover save!) ...but as you state specifically in the rules that the hero never confers his movement bonuses over onto other models that he joins I wanted to make sure.

Thanks!