But if you are buying a lot of the bits, lifeboats, vents, lifebelts, not to mention the hull then it isn't really scratchbuilding in the sense of the word is it? To some extent your are assembling your own 'kit'. Plus a lot of the items, glue, paint, R/C gear & motor would also have to be bought if you were making a kit.
I certainly don't want to get into the 'what is scratchbuilding' controversy again but surely it does involve making most of the model from what might be termed 'raw materials' including the fittings.
The reality is that you can choose to build a wide spectrum of options from 'full kit', through various varieties of 'semi kit' until you end up at the point where you are making your own studded anchor chain. At what point this becomes 'scratch building' is a moot point and I doubt whether any two people would fully agree except to the extent that it is somewhere in the range where you have built the hull, superstructure and a good proportion of the fittings yourself.
Colin