OffSystem is based on a totally different algorithm than RetroShare file system:
RetroShare: F2F architecture, multi-hop file transfer, files are stored explicitly
OffSystem: global network, single hop file transfer, files are split with random xor and stored as (factorized) chunks of random bits.
Although we could easily broadcast offUrls within RetroShare networks (such as in the link cloud), there's no point in using the xor-split format of files, because RS is already anonymous after 1 hop. So it would be a 50% waste of bandwidth. Combining OffSystem and RetroShare is therefore not likely to happen.