The picture is used on the cover of Winning Karate by Joseph Jennings.
My guess is that that stance is from some kata, and as such it could be completely reasonable.
But, your critique is of the utility as a general ready stance for fighting, and you're inviting us to join in...
As far as that goes, you're right - it would be terrible if used as a general fighting stance, and it's a good skill to read weaknesses in a position if used during sparring, so here's some analysis:
- as you say, the back hand is effectively out of play
- stance is too side on
- further removing the back hand from play
- the back leg is pretty useless too, as it can't take the proper line into a front , side or turning/roundhouse kick
- the hips/shoulders have no room left to rotate in behind a front jab
- the front hand could not comfortably or strongly be brought from his right to left in an inward knife hand or reverse knifehand/ridgehand strike because it'd have to be awkwardly extend outside the line of the shoulders first
- similarly, the front hand can't strongly block any attack coming in from his blind side, such as an opponent's inward ridgehand, turning/roundhouse kick, spinning heel/hook kick, slapping/crescent kick (soto/uchi mawashi geri)...
- the front arm's too straight and out of position - it would have to be pulled back a long way first before a decent jab or block could be executed
- we can't see the leg position, but if the front knee is turned too far inwards, it's especially vulnerable to a stomp at the knee; if it's inline with the shoulders, a low turning/rounding/mawashi-geri forcing it further outward could be very unpleasant
That said, I have seen some extremely good fighters (e.g. Tsukamoto Norichika of Shin Kyokushin) extend their front arm vaguely similarly when fighting at long distance... perhaps as a way to help gauge distance and perhaps for complex reasons of balance and mobility.