I usually play 1500 pts, but anyways, it is not hard to hide a commander, at least not where I play. If you use the terrain-guide
GW gives you in the
BRB, there should be
LOS blocking terrain, and then you are only shooting
SMS etc on me, and won't manage to reliably kill my commander for at least 2-3 turns.
I would also never take first turn if I had the chance, ninja Tau always want to go second. (unless there is no
LOS blocking terrain on one side - shouldn't happen too often) If I had first turn however, I would certainly take the side with some
LOS blocking terrain.
It seems you have found one weakness of the tactic (commander dies), and yes, that messes with my plan, and I have to fall back on mech-tactics, and I will have a harder time. All players recognize that my commander is the linchpin, I even tell them before the battle what his equipment does if they don't have full control over Tau armoury. As I have said many times however, killing him is not easy to achieve, ninja players know how to hide

Very fast close combat units is all I fear, and especially those that don't have a transport (bikes, destroyer-lord etc).
You must also remember that even if I loose my commander, almost all my units are geared to hit really hard when they enter. You will have lots of suits dropping in and blowing up tanks and flaming infantry, kroot charging in from the flanks etc. You will probably still be playing in reaction to me, as I choose where to fight. That way, I can stack the odds on one end of the field. I get the bonus of knowing where all your forces are, and I have the mobility to engage you anywhere on the field.
It is hard to theory-hammer this, as there is little math involved. You obviously have little faith in this strategy, and that is fine, but I still advice Tau players that are struggling to win with conventional tactics (which you apparently don't), or players that just want to play a challenging, but powerful strategy, or players that just don't want to spam stuff, to test this strategy. It is highly rewarding, and it has a lot of potential in the right hands.