Snags Vs Maintenance issues, minor problems or urgent ones...since when is it subject to pilot's discretion before dispatch?? The manufacturer will have produced a MMEL for your aircraft and your operator will have produced a MEL based on it. That book clearly tells you what is major or not, and what can be deferred and for how long. Extensions are also possible. The operation can continue to run smoothly without delay or cancellations even if you do things properly.
So why not simply write down a airflow vent and have maintenance defer it?? Now, if the MEL says you can't fly without some inop items but you choose to do so anyway....time to reassess your judgment and contemplates the possible consequences....it's your signature and licence on the line.
carry a flight engineer on every flight - he does have the final say!
You wrote a good post, but just wanted to add to your above statement that it is the PIC that clearly always has the final say as to whether accept to aircraft or not, and not FE. You don't have to be a mechanic, but only be able to read the MEL...