Shiftout over I2C possible?

[tumbleweed]

Won't all these slow down your data communication?

Boy. that's an understatement!

You'll have to do three I2C writes for each bit (set data, set clock high, set clock low).
It'll be as slow as molasses, but it'll work (as long as the APA102 isn't finicky about the SPI timing)

Obviously you can't use Shiftout to do it.