Well, personally I only expressed mild disappointment, but quite frankly I don't think I like the idea of a storyline where random time-stopping ninja maids with no backstory have a place in the story.
You're already judging the story being random without knowing even what ZUN is going to reveal us. How can you judge something that isn't yet there?
Also, what did she have to do with PCB?
Preventing the SDM from starvation.
Seriously though, speculations are one thing. Judgements are groundless without proper information. Logically liking Sakuya as a touhou is different. Has nothing to do with th14. People can like characters or not, fair enough.
Edit: I see several people posted before me.
Edit2: You see, not everything has to have a reason which leads into a ZUN.wav (bang). Whether you find the reason for Sakuya's involvement in PCB interesting, funny, boring or hateful is completely your own opinion and possibly valid. After all, subjective = subjective