My apologies for discovering this discussion a little late...
Disclaimer: I am NOT well versed with hosting/transferring files via HF, MU, or some of the other hosts mentioned here.
Having stated that...
In order to perform the equivalent of a "remote upload", doesn't the destination file host simply need direct unguarded (nothing fancy) access to the file in question?
If that answer is "yes" then any of these might be viable solutions:
A) Upload the file once to an independent FTP site and then have each final destination access/transfer/host ("absorb") it directly from there.
B) Find a free/generic web site hosting service to post the file initially. You can then use that direct link to allow your final destination to access/transfer/host ("absorb") it directly from there.
C) Enable web services on a local machine, move the file to a web-shared folder, and then have each final destination access/transfer/host ("absorb") it directly from there. Yes, this is less efficient than A or B, but you could (possibly?) queue the transfers and batch execute them during idle time.
In other words, instead of trying to navigate/transfer files to/from HF, MU, RS - would it be easier to:
1) Upload the file (temporarily) to some alternate very generic easy/direct access place initially (not RS, MU, HF).
2) Have all final destinations (RS, MU, HF, etc) access/transfer/host ("absorb") it directly from that very generic easy/direct access location.
?
Each of you might have specific/individual concerns with A, B, or C above - so each individual's question might become - "Are there any
neutral (non-RS, non-MU, non-HF) locations available to me where I can temporarily store my files?".
Just thinking out loud, while we all patiently wait for forumophilia to be the first forum to come up with an "FTP hosting plan" for dedicated members... j/k
Seriously though, eons ago, there used to be tons of open FTPs, and there used to be tons of generic/free web hosting sites available that would have easily served this very purpose. Such sites may still exist today, but I don't have the necessary resources to investigate/test.
Best wishes.