Would it be better to go down the meego/nemo route of putting the whole OS on microsd card?

This way you could get away with not optifying things, as you have as much space as you need. Apparently the performance of the emmc isn't that great, and when you factor in the limited number of write cycles flash memory has, everything on microsd might be the best way forward. You could then use a bigger Compcache to improve performance.