If priced right (much lower than the insane pricing of the one mini 2), I think they could have a successful device in this. Sure, its still plastic, but its not THAT bad looking. I got the chance to see the one mini 2 in Phones 4 U today, and I was really disappointed by the design. There's a limit to how big bezels should be and trust me, it surpasses those limits by far. This made it actually look ugly from the front, which is disappointing for htc.
As for the S5 Mini, I think the specs should be as followed:
-4.5inch 720p-1080p display
-SD600 (although they'll probably use SD400 like all mid rangers do nowadays).
-A decent camera- megapixels don't matter as long as the camera is capable (8mp seems fine, like the Note 3 Neo).
-2,500mAh or more battery.
- Good quality speakers. I doubt they'll improve the speaker over the S5, but this sort of applies to samsung phones as a whole- they need better speakers.
ugly, thick bezels, Samsung needs to fire its entire design department..