I agree that plane3.gif looks the best. The only thing I would change is to make the engines a little bit shorter, so they don't stick out the front of the wings so much. They can be almost flush with the wing, like they are on skylander-02we.gif.
The larger one.. I don't know.. To me it looks too long and skinny, the 2 pairs of similar wings look like too much (and the intake of the rear engines is right in the exhaust of the front ones, which is more of an issue than one might think if the worry of VTOL aircrafts choking their engine because of air recirculation still holds).
I am also not sure it is warranted. The avenger carries 26 troops at most and it is the Ultimate Craft. Of course, it might be considered so because it is at once your best fighter and your best transporter, so one could argue that as your "best fighter and pretty good transport", it's still the ultimate craft but I am not sure it should be outdone as a transport. I am finding the the skyranger's 14 troops is most of the time enough (in most of the UFO missions, some of my soldiers end up just walking along not finding aliens, or picking their while my breachers clear the UFO. Bases and terror missions are different, but not that different.
A conventional plane carrying 16-20 soldiers should be enough, I think. It is then an upgrade on the skyranger, but also leaves the avenger as the ultimate craft. I am thinking of going:
1 - Skyranger (14 troops)
2 - Alloy Skyranger (16 troops & faster) + smaller plane (10 troops & a fair bit faster
3 - Hybrid Skyranger (uses Alloy + UFO Navigation; 18 troops and faster than alloy large plane)
+ smaller plane (12 troops and faster than the alloy small plane).
Of course, the small planes will be outdone by the lightning once it becomes available, but until then it is a great craft to quickly go to a small landed UFO before it takes off again (and they can take a HWP). Similarly, the avenger will outshine the larger planes, but that's the point, it's the best craft.