Hmm. I'll go with...
1. Delays on AGA - Sure, AGA wasn't a game changer in late 1992 when the underwhelming A4000 appeared, but the A3000+ in early-mid 1991 could have made a difference, especially with the 3000+'s DSP.
2. Repurposing the A300 as the more expensive A600. A product line with an A300, A1200, and A3000+ at the low-, mid-, and high-end market segments, respectively, could have been very competitive
3. No PAL Video Toaster. Imagine if the already-strong Amiga market in Europe were given a shot in the arm with a catalyst for a whole new productivity market.
