Let me clarify: it might have reducing the pricing pressure that resulted in the low-end Amiga models that we actually received. The A500 and A600 would no longer have been Commodore's entry level computer models. And as such, with more upward flexibility in pricing, they could have had better specifications.
The Amiga 500 had a bloody great specification for its time. The Amiga's problem later on was that C= rested on their laurels too long and didn't invest enough in developing it until the PC had caught up (even if the latter's architecture and OS was still horrid) and the Mega Drive and SNES matched it for 2D parallax gaming.
In particular, the A600 might have come with a faster processor, more memory and a full keyboard.
As I mentioned, the A600 was (AFAIK) meant to be the A300, a cost-reduced budget machine. If it had been something else it wouldn't have meaningfully been the same machine. More importantly, it only really existed due to the past success of the A500 years previously; any high-end "A600" in your alternate past-future wouldn't be analogous to the one we saw, except in name!
Speculating as to what the A600 might have been therefore isn't just pointless, it's meaningless; like asking whether Germany would have won WWII if the Roman Empire had never existed. Europe- if not world history- would likely be totally different, a state analogous to Germany might not even exist, the politics would be totally different, and it's unlikely that the Nazis would have risen in *that* place at *that* time in that situation, so even WWII itself wouldn't have existed though other conflicts would have.
Perhaps. But one reason why such a series would remain successful would due to software momentum. Remember, Commodore's super-budget computers were really popular in places like central Europe. If the Amiga doesn't have a large base of software written in Hungarian, but the 8-bit series did, do you think that they'd be more apt to purchase a used A500 or a new C512?
They probably wouldn't have been able to afford a new C512. And (if it was cheaper but less capable as implied), C= would have been foregoing many people who bought- and *were* able to afford- the Amiga in Western Europe (making it the most popular computer of its era) for lower-value sales in Eastern Europe. And I'm not convinced that they wouldn't have preferred a used A500 unless the C512 was really close in spec.
Anyway, this is all getting rather academic and speculative, so we'll just have to disagree on this one.