It is strange, that you do not want us to post the best solution by using a cell array. Unfortunately you only claim, that "it does not work", but do not mention any details. Of course it works, when you add a little "{:}":
v = {fts1,fts2,...,ftsn}
newfts = merge(v{:})
Then merge() gets a comma-separated list exactly as if you call it as:
newfts = mergs(fts1, fts2, fts3); % Or how many elements v contains
In addition using a cell is a much better idea than naming the variables "fts1, fts2, ...". Using fts{k} would be more convenient, see http://www.mathworks.com/matlabcentral/answers/57445-faq-how-can-i-create-variables-a1-a2-a10-in-a-loop.
