OK this is a tedious task!
I found the great http://renamewand.sourceforge.net and used it to rename FTL templates. I'm not sure I used the best method, but I got some result (see svn.st attached)
Here are the command I used
java -jar ~/tools/RenameWand22/RenameWand.jar -r "<a>.ftl" "<FN.spaceout.pascal>.ftl"
java -jar ~/tools/RenameWand22/RenameWand.jar -r "<a>.Ftl.ftl" "<a>.ftl"
java -jar ~/tools/RenameWand22/RenameWand.jar -r "<a>.Fo.ftl" "<a>.fo.ftl"
But this only capitalizes (put the 1st letter to uppercase). Because if we have a filename like minilastproductsearches.ftl we have no ways to automate the process :/
There are a lot of files like that and most are under specialpurpose/ecommerce/template/ (147 templates at all) where it's a real mess with underscore separators as well. So unfortunately apart doing it there by hand ...
Then comes the most tedious (and risky) part: renames files in code, where they are called...
I wonder now if this task is realistic...