The III's II compatibility mode ramps that down to 1MHz, and has other restrictions to make sure that II software cannot use any III-only features.
Without III sucking up all of Apple's R&D budget and attention c. 1979-1980, the Apple II would surely have seen earlier enhancements. The II+ (1979) would likely have had lowercase and better keyboard (which did not occur until IIe in 1983), and a new model in, say, 1981 might have shipped with an optional Apple 80-column card (again, with the IIe in actuality). Built-in 128K RAM probably would not have occurred until 1984, akin to the IIc's introduction, but earlier support for RAM expansion alongside 80 columns is possible. One of these models would likely have had the 2MHz clock, too, while no II in actuality shipped with a faster clock until IIgs in 1986.
I never felt the IIgs to be an actual Apple II. It feels like a different computer that can almost accurately emulate a //e or //c, but has that inelegant impedance mismatch between. I also get the same impression from the Commodore 128, but feels even worse that it needs to drop to 1MHz to use the C64 video modes, and don’t even get me started about its Z-80 side.
