I think the second one sounds terrible, all those mentions of 'person' do not sound good stylistically. The problem comes because some of those nationalities aren't used to describe a person by themselves. Some of them are but there is a problem with a French, a Chinese, a Japanese, and perhaps a Nepalese. For example,we say 'a Frenchman, not a French. We also don't say a Chinese and a Japanese, we normally say 'a Chinese person' or 'a Japanese person.' But saying these would alter ruin the style somewhat. Here is my suggestion to re-write this: Before this reorganization, the panel consisted of an Italian, a Belgian, a Russian, a German, an American, a Canadian, an Australian, a Ghanaian and one representative each from France, China, Japan and Nepal. Although maybe it would bee better to be consistent and just refer to them all as countries. Before this reorganization, the panel consisted of one representative from each of the following countries: Italy, Belgium, Russia, Germany, the United States, Canada, Australia, China, Japan, Nepal and Ghana.

Both are ok. However as there are a lot of different nationals on the panel I think the first sentence sounds more natural. As a native speaker we would not keep repeating 'person' as it is too much effort!

To me, the second one sounds better, even though it is longer. This is because the "-ese" demonyms of countries (Japanese, Portuguese, Chinese, Nepalese etc) are not usually used on their own. I would say "A Japanese person/a Chinese person". I find this quite arbitrary. Theoretically, they should be as valid as "A German" or "A Canadian" but they simply sound unnatural and there seems to be a lot of uncertainty regarding their correctness. Also, a French person is usually referred to as "a Frenchman/Frenchwoman". As is often the case with language, it is partially a matter of personal preference.

I agree with Paul's comments and think he has made very helpful suggestions below.