Distribution of Objects between files

I have a new requirement that is dictated by the software applications that connect to a particular DB which is a 10gR2 DB. These two applications uses tables of their own and there are a few tables that are shared between them. All of these tables are located in one tablespace and both applications are using one connection string to connect to this DB.
But now these tables are required to be separated physically. I know that I can have a tablespace with multiple files scattered across multiple disks or servers. *But can I enforce the location of a particular table? Could I restrict a table to a datafile?*

*My second question is that would it be possible to take one of a
tablespace's file down (i.e.: make it offline) and still commit transactions in that tablespace as long as they don't have to read/write anything from/to any of the objects in that file?*

*The whole idea is to isolate the tables of one application from another in
separate files so if one file becomes inaccessible the other application continue to work.*
However, I don't want to use multiple tablespaces. Because then applications will have to change to handle distributed transactions between tablespaces, let alone reading and joining tables from two different tablespaces.

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