I take back what I said about a major rewrite. Everything you want to do I think can
be done under the hyperdb level that roundup uses to access the database/filesystem.

This may be doable using the dbm backend, or creating a new db backend. There
doesn't seem to be any requirement in the code for sequential numbering of objects
that are stored in the database or on the filesystem (messages and attached files).

Internally object id's are type string. But I can't guarantee that there
aren't conversions to integer in some places. The use of strings for ids does cause
the code to be slower than if we had used integers originally. But I don't think
the code is going to be rewritten the change from string to int for id's.
I know I am not going to do it 8-).

A bigger issue is how the vcs backend does locking/isolation to prevent parallel updates
from being committed where one of the updates isn't complete. Currently in Roundup
the database is locked (dbm) or runs changes inside a transaction (sql backends) to
prevent parallel changes from mixing.