Memo file should be opened by application in filesystem terms all the time a file is shown as opened in GUI. And editors should write protect files they are working with.
Aside from protection from concurrent edits by different applications this way of working with files is semantically better and therefore resolves different issues.
For instance, currenly memo pad can't delete new memos. Steps to reproduce:
2)Type a couple of chars
3) Try to delete the file.
You'll get error "Failed to delete this file" (because there is no file yet).
I believe this approach would simplify handling of memo names collisions.
I have not developed for android, but I believe this is an example to start with.