Single sided doesn't always mean less complex. Take the LD-S2 for example. If something ever goes wrong with mine, I'd probably faint. Just getting it disassembled to the point where I could clean and apply new grease to the tray roller was awful.

The LD-S1, LD-S2, HLD-X0 are obviously edge cases though. Maybe throw in some of the older players like the CLD-900 (I haven't opened one up but it doesn't look fun).

The CLD-S201 I'm a fan of. It sits before the CLD-S104 (which has the most fragile M-Holder), but after they stopped using the white rail that always cracks (CLD-1070, CLD-1080, etc). I actually was working on a player where the piece of the rail that is usually partially cracked had completely broken off so the pickup could no longer traverse before or after that point.

The biggest issue with single side players for me is almost all of them lack CLV trick play.

Yeah, after a certain point Both Side Play was the main feature people wanted. Nobody wanted to flip discs. Beyond that came all the other options but after 1991 or so every player was either Both Side, or super high end or super low end.

There is the Elite CLD-31 (a CLD-1090 with minor upgrades) which I guess would sit in the lower middle range. Better audio than a CLD-S201, and you get optical out.

The CLD-S304 is the only single sided player outside of the HLD-X0 that I know of that has AC-3 RF out.