When rotating masts you lose the detail found in the Airfix type - so you have to replace the mats (I am trying to work out the operating of the yards at 1:180 on Airfixs victory - resuming sometime in the next week
), their scale is usually too small to be realistically feasible for operating effectively and expensive if you go say for the larger Heller victory, clippers and the like are at scales in the 150 - 200 range and extremely top heavy so the sail board is a must and then it pulls the vessel down so the controlling equipment has to be as light as possible.
me, size is also an issue for transporting, the most common subjects appear to be warships and tugs then fishing vessels, then novelty, where what I would like to see is some of the more industrial vessels - now this usually means a lot of offshore oil, very few ferries, though Carl has been working on two exceptional examples and train ferry no 3 is also a classic project.
Mearsk style carriers are bulky to transport as is others, the Apache tanker is looking like a good project to follow and distinct.
Brockelsby and similar fine detail masterpieces are all a dream to watch, but out of my skills range.
As for Airfix style kits - always, its easy for me to convert than build from scratch, but that's not proper modelling - that only comes with altering the basic by adding detail to make it special and fix what the kit supplier has only hinted at - I know some will disagree, but why supply a brass etch part if the actual kit is supposedly a fair representation - because its not - its only good due to the amount of detail it can represent at that scale, so in most cases, a semi kit with the hull prefabricated and the basic superstructure is a cost effect way of a kit.
Cost is only relevant as to how much an individual is prepared to pay.
In conclusion - what subject is interesting, has not been fully modelled and can be done without taking years and masses of cost to the modeller.