Would a big drop of thermal compound on top of a SMD component ( without adding a heat sink on top of it) improves its thermal?. I wouldn't expect a big improvement without a heat sink, but would it make a little bit of improvement?.
Doubtful, you would only be modifying the surface convective heat transfer while adding a little thermal path length. No idea whether bare or wet is better without data.
If you need to improve convective heat removal, might think about JB-weldvane a wee bit of aluminum bent to fin,-like ( I'd bet somebody sells little "hats" for SOICs but no idea who or what they call 'em; might also think about cutting down a bigger one from the reclaim box.
Basically you think that without a little heat sink ( even if it is just a fin of a smd heat sink) it won't make any difference, right?
My problem is that the PCB will be mounted vertically and it will be under vibrations...., therefore fitting a heat sink make feel a little bit nervous.
Do you think the JB-Weldvane would glue the little piece of aluminum in a way that it wont drop at all?
What is the component?, do you know you can get insulating SMD "resistors" which very well transfer heat to a copper plane, even if that copper plane is at a different voltage to your SMD pin being cooled.
You can also do "vias in pads plated over"