Amendments are very restricted after Final
When filing an Appeal against a Decision of Rejection, the following restrictions are imposed on amendments: new issues which would require a further search cannot be presented, as is the case in the U.S. practice after the receipt of a final office action; and adding a new element to the claims, removing a currently existing element from the claims, broadening or changing the gist of the claims, and increasing the number of claims are impermissible.
Also, if amendments do not make the present application finally allowable even though they make the claims patentable over the references cited so far, or if amendments create a new ground of rejection, such amendments will be dismissed by the Board of Appeals, which will most likely result in an unfavorable Decision of Appeal.
If the claims are to be amended to the degree beyond the above-mentioned strict restrictions on amendment after a Decision of Rejection, it will be necessary to file a divisional application in order to have such amended claims duly entered and examined, like an RCE after a final action in the U.S.
Please further note that allowability of the application will be judged on Appeal in terms of whether or not all of the claims are patentable. In other words, if the application includes at least one unallowable claim, the whole application will be rejected even if there are some allowable claims in the application (i.e., a so-called all-or-nothing approach). In Japanese patent practice, the claims are not treated individually on Appeal, and the application will be rejected even with only one unallowable claim. Therefore, it is necessary to ensure that the application includes no unallowable claims when filing an Appeal.