I did briefly skim it, but seeing as how your arguments sprouted from my wish to talk about realism i decided that they didn't apply to me, because i don't want to talk about realism. And realism, is the effect that a game reflects real life, and invovles a lot pointless quantifying of scale, that never adds up. Thats why i do not want to talk about wether or not civ 5 is realistic, the argument is pointless.
However all ships in civ are built on land (usually inside costal cities) and now in civ 5 on the coast as your units embark, this is all I was saying.
But if you really want to talk about how realistic unit embarkation is, fine, in the many years a single turn of civ represents (realism alert) its entirely possible to buil d enough ships on the coast to embark your army ready for sea travel. (of course as is the problems with realism arguments, the fact that a turn represents many years, then begs the question how come you can only build one wall of a granary in those many years inside tokyo?, and how come you can't travel more than one hex which clearly represents 250 miles?, a unit moving a 5 mph, could clearly cover more territory in that span of time.) (i hope you see my problem with an argument on realism now.)
When i was talking about shipbuilding on land i was simply referring to that ships can't be built on water, the parts float away and sink, this isn't an argument of how realisitc the game is, but how shipbuilding works. So having ships plow a few fields as you say, seems totally acceptable to me, i would naturally prefer to see some workers build a ship and then roll it down some logs into the water, but thats an amazing complicated and time consuming animation.