There is not a way to tell fschange to index the files in another method. However, you can call props.conf to tell it to uncompress files. You'd do something like this:
[your sourcetype] CHARSET = SHIFT-JIS NO_BINARY_CHECK = true
[source::D:\samplelogcompressed\test\*(?
For details see:
http://www.splunk.com/base/Documentation/4.1.5/admin/Propsconf