It would also be handy for beginners to output an int without having to bitshift high and low bytes - somewhat tricky since it has to be done differently with MSB and LSB schemes.
Somehow the framesize option found it's way into the Basic Stamp and other easy-to-use micros. I think the BASIC Atom even implemented some clock control options.
As to the SPI hardware - I haven't puzzled my way through this, but would love to see this implemented in shiftout asap.
But it would add another parameter to the function, that has to be documented and explained.
Since ints and ints are so different nowadays (2bytes - 8 bytes long)
Odd frame sizes is only a tiny edit to the code and is rare so I dont see any point to building it in.Anyone requiring it can easily do it.
I think a library for Hardware-SPI would be a good idea, and should not be to difficult to create.