I’m only as knowledgeable as what I read or find, my knowledge is where to look for records NOT necessarily the subject matter.
Sorry, I can offer you nothing on Karl Epple except to say that, unless he was captured, if he was part of Napoleon’s forces any records will be in the archives of the French Ministry of Defence. There was a notice about problems with a database of Napoleonic soldiers being created on the site athttp://www.memoiredeshommes.sga.defense.gouv.fr/index_en.htmhttp://www.memoiredeshommes.sga.defense.gouv.fr/index_en.htm , the French Ministry of Defence "Memorial" site, all that’s left of that is the picture!
Soldiers’ records in archive are filed by regiment and without that you can’t even begin to search. Also the French only permit professional researchers to access the files. I did have an English translation of the archives guides but they were lost some time ago and I can't get back to the site where I found the french version.