Yeah, you gotta wonder, Rick. The Rogue One book I just picked up provides something of an explanation (a cutaway) for the foils as a form of repulsor lift tech that provides for a more agile craft, especially in the 'landing zone' environment. Obviously, the design isn't really aerodynamic (like a brick!), so the moving foils present a concept of adjustable force vectoring with a way to reduce the footprint when landed. As for the length, they certainly went with the 'what looks good' principle, though proportions remind me somewhat of Darth Maul's ship.
The TIE-SK (Striker) is another case in point though the prevalence of TIE 'wings' as 'solar collectors' is a truly bogus nomenclature. For one, how would that work for vessels intended for deep space operations? (It wouldn't) More reasonable is the wings are used for force vector manipulation and also perhaps for heat management. They would definitely not be an asset in an atmosphere for anything but a straight-line path... and wake turbulence would be a real problem!
I do like the SK as a two-man assault escort craft; sort of like the Huey gunships. Plus, it will be relatively easy to model since it is essentially a TIE 'ball' cut in half with a tube inserted between. Just for grins, I picked up the Hasbro Striker toy from their 'value' line & sold through (in the US) Big Lots! & Dollar General 'thrift' outlets. I didn't find any at DG stores in my area but hit a couple of BL sites & found a couple. I thought they might fit in with my 1/48 scale TIE selections (AMT, Estes, MPC...) but the toy is 1) simplified in detail & 2) undersized if the TIE ball diameter is assumed to be constant. The Disney sourced length spec seems too large so this may become an "eyeball" project for me...pun intended! The toy's proportions look good, so it may work as a reference. It is a pretty well made toy, but compromised further as a replica by simplified (read 'inaccurate') wing hinges and missing under-belly 'bomb dispenser' features.
Anyway...
Regards, Robert