I think Queen Mary has about 2,000 portholes in all so good luck with that. One of my ongoing projects is a liner at 1:150 scale but I'm not even going to attempt to cut out the portholes, I shall just punch them out of dark blue trimline tape and stick them on the hull using masking tale as a temporary baseline. It will give a neat effect rather than an ambitious uneven row of ragged holes! A leather punch will do the job and it should be possible to fabricate the oval ones by squeezing the appropriate cutter in the revolving punch.
I agree that having all the portholes illuminated would look good, but only if you can make an almost perfect job of it. Apart from getting the size and positioning exactly right, you need to remember that on the real ship the portholes were fixed in plating around 12mm thick. At 1:192 scale that would be 0.06mm ship side which is not practical. Assuming that the sides of your model are between 1.5mm and 3mm that equates to around 1 to 2 feet in full scale so your 'portholes' are actually more like rabbit holes.
As a final point, given the huge amount of work involved in cutting out those 2,000 holes - just how much time will your model actually spend illuminated for people to admire? in short, is it really worth the effort?
Colin