There are Xperia 2011 devices which have a working Sailfish OS port. To be honest it works surprisingly well (as for such piece of hardware) but has also some issues. Mostly with scaling (320x480 devices especially, mostly with 3-rd party apps), lacking of the proper hardware keyboard layout and the amount of RAM memory seems to be a significant bottleneck on daily routine using.

I am also looking for a "preferably smaller" device with Sailfish OS porting in mind. Unfortunately, all the Nexus devices lack the memory card slots.
Currently I am thinking about Sony Xperia Z1 Compact and Motorola Droid 4. The first one seems to be almost perfect. Has even the FM transmitter. But doesn't have the hardware keyboard and has a poor CyanogenMod support. The second one has a lot worse hardware but includes hardware keyboard. The CyanogenMod support seems to be better.

It seems that every available solution is to some extent a compromise. And that bothers/annoys me.