SQL CE does not support Stored Procedures therefore our existing SQL data layers will not work with it. (There may be other barriers as well). It would require creating and maintaining a data layer specifically for SQL CE. It would certainly be a big job to make an initial implementation and a long term commitment to maintain it. It is not something that I would want to implement or maintain.
SQLite is a file based db that could work well for offline, but how you would sync it with a server running MS SQL or any server db for that matter is not something I know of a solution for.