Posted Tue Nov 29, 2011 12:37 PM
Looks entirely doable to me. There's rarely more than two moving objects per row (or even on screen) and the backgrounds could be done using an assymetric scrolling playfield.
It might need more RAM to hold the playfield data to enable scrolling. You could perhaps make a rather clever kernel that rotates the data into a line buffer, like the rotozoomers in my most recent demo does. That'd probably mean an 8 line kernel (approx). Then your biggest concern would be ROM for the levels.