Okay i got a strange plot bunny, blame sleepderviation but how about the Fate Heroins as a bunch of household faeries that Shirou somehow gains and that now try to "improve" his life. Can you really resist a flying 10 cm/4 inch winged Harem that tries to set Shirou up with someone before maybe falling for him? Obviously that would go for the Cute/fluffy angle.
And at least the Fate cast would be better then the Tsukihime cast because those as household spirits would be really strange. And Kohaku would be far to effective as a Unseelie