Lack of playstore is the easiest thing to come around. The only real issue is if you need something that simply doesn't work without play services. While a lot of apps will say that the device does not have them they will still work just fine. But some just won't work.
The second issue is if you need some kind of car integration. While basic stuff like phone/contacts/A2DP work just fine in AOSP and problem is usually on a car side. mirrorlink is not avalilable on custom ROMs. But it's not there in sailfish so...