Interesting points. I must disagree though.
I am a fan of the notion that being too specific and compartmentalized in terms of defences against ‘x’ attack invites hesitation. Therefore I view the headlock shown as a variation on the “front headlock” theme, just as the guillotine choke is a variation on the same.
With regards to the above drawing, which to me is only part of the wider picture, it is an example of a poorly applied front headlock. Assuming both are unarmed, I’d say that the guy in the headlock, provided they have reasonable grappling (by which I mean MMA/BJJ etc) experience, can easily gain the advantage.
I do not think “sport fighting rules” come into it. Sport fighting, by which most people mean MMA, includes the guillotine choke from that basic position which is a hell of a lot more effective than most things.
For a start the guy applying the choke has a poor base and the guy in the headlock could easily effect a takedown into mount, from where he could extract his head and ground-n-pound the attacker. Before you jump onto my suggestion of taking it to the ground, bear in mind that we are talking about going straight into a dominant position.
The above escape is not typical in MMA et al because people generally maintain a better base whilst applying the headlock. Therefore we should consider whether the other “sport” guillotine escapes would work here. Firstly the tactic of looking/pushing your head up behind their shoulder and circling around behind their back – yep, that would work and leave you in a dominant side/back position.
Or the escapes where you lift and slam the opponent – requires greater physical prowess but no reason why it suddenly doesn’t apply equally here.
The dropping defence I would personally count last but I am sure it could also work with a high degree of success if you are suitably skilled.