Could Commodore have made a financially successful low-cost Amiga laptop circa 1991 - 1993?

I can't say definitively but based on my experience in 1991 with a 68K-based PowerBook 100 I doubt it. Even with a 1-bit monochrome display and no custom co-processors executing in parallel the battery life wasn't great. Also, most LCD screens don't support some of the weird field/frame and timing things the Amiga could do with CRT displays. Even rounding up from 59.94 NTSC field rate to 60 fps would have caused some Amiga software to have display issues.