The limitation is in the total width of sprites per scan line (which I suspect is what you was getting at, even though you wrote 16x16), but this can be supplimented with bobs. With some proof of concept code I was fooling with I simply read the total width of sprites per scanline and when that exceeded 64 I instead used bobs (or just wrote to bitmap, depending on what the graphic was,... sometime bobs arent needed and overwriting bitmap is quicker).
AGA of course in theory can have 64 pixel wide sprites per channel, which with multiplexing is enough to have next to no restrictions. Unfortunately the theory and practice here dont match 'cos Commodore screwed the hardware up and instead gave us near unlimited sprite power that is drawn off the physical screen :/
Interesting thread though for my tastes. Im currently on the lookout for what to work on next now that my Jooleem offshoot is nearing completion (graphics and sound are still needed, but its easy enough to add/replace them whenever I feel the urge).
Something Zelda-esque, or some sort of RTS type game are what Im considering, being that they both lend themselves well to the Amigas hardware. I have some skills, but Im no hardcore asm coder, so am on the lookout for stuff that's both a good match for the amigas custom hardware and the sorts of specs that are common these days for classic users.
Probably favoring a RTS type game, soley 'cos its something that could still be playable to the coder (zelda-esque adventure game could be a little boring to play back when you know the game inside out).
