100s of devices on SPI bus with daisy chaining - theoretically possible but who's done it?
I think you're good to go. A few points I noticed tho'...


your SDO requires a pullup. So clock speed needs adjustment accordingly (see datasheet) 
the 'mega SDO will be driving 8x chips, but I think it should be ok. 
use standard best practices in terms of  PS decoupling and layout. 
datasheet mentions SPI 'compatible'. I could not quickly find where the differences are, other than non-8 bit codes. But since you are daisy chaining 16,it shouldn't be a problem. 
Max speeds will depend on your trace lengths,  so derate speeds accordingly. 
You'll have to ENSURE exact number of bits/ clocks,  otherwise your chain could get seriously messed up ! 


Cheers