Ahm. Definitely not a stupid question, because using a "sideflip-case" and watching a video by holding the q in one hand is definitely not comfortable without turning the device. Would love the option too.
It is worth noting that because the Q10 does have an accelerometer, the phone can "rotate" a rotation lock for BBM video would be handy as if anyone has noticed, a Q10 in portrait and landscape has a different camera aspect ratios and sometimes it does get slightly annoying.