The A1200 could have come with 28mhz 020 and fast ram. It was dropped to cut cost.
They could have released the A600 as the budget system, there weren't many AGA games anyway. Make a few game accessories for it, e.g a numeric keypad.
Then release a 3MB A1200 with fast 68020 price should be $1400. $1600 with hard drive. No further upgrades necessary.