Try a broadband router that has the possibility to use 3G for the upstream. They have an USB port for the dongle, and then provide "internet" over WiFi and/or Ethernet. Can't recommend a certain brand or model, but there are plenty available and they aren't expensive either.

We equip the BeoSound 5s we install on boats with WiFi so that they can join mobile hotspots. We've found that transferring content is actually pretty speedy this way. SW updates are slower than at home, but not too terrible. 

If you have a Beosound 5 on a boat, surely you do have an internet solution also? 

Anyway as said here I also suggest a router with support for mobile broadband dongles. The BM5 can be connecter with a ethernet cable to the router. Another more temporary solution would be to share your computers internet connection to the BM5. If you have an iPhone and a Mac it is easy to do.

Another solution could be to carry the BM5 into their home and upgrade it there perhaps. 

I would install a wired setup in the boat and use a router or routermodem with support for mobile networks, connected with several wifi-access points around the boat for easy access to the network with good internal speeds. 

If your friend is traveling alot in different countries they can buy local prepaid simcards in most countries that will work very easily but probably require a little computer skill since the network will have to be set for the current ISP. 

Another thing could also be to add a server to cache internet traffic so that it can be served faster instead of being downloaded several times over again. 

A simple solution is to use the "connection sharing" mode of a smartphone (iPhones an dAndroid can do it, depending on your provider), which creates a wifi hotspot powered by the 3G network.

Yeah I kind of agree with Bsantini here. Whilst there's no way on God's earth that I would ever recommend a BS5/BS5 Encore, I think a BeoSound 8 with the iPhone or iPad would have been great here! Why make life complicated?

Paul W wrote:

Yeah I kind of agree with Bsantini here. Whilst there's no way on God's earth that I would ever recommend a BS5/BS5 Encore, I think a BeoSound 8 with the iPhone or iPad would have been great here! Why make life complicated?

It might come as an unpleasant surprise for you, Paul... But... (I don't know if I dare to say...) 😮 
Well...Let me break the news...
 
Not everybody in this world own (or wants to own) an iPhone or iPad...😉 👍

-and some even wants a system with some quality speakers, instead of just a dockingstation...😐

Steffen wrote:

Not everybody in this world own (or wants to own) an iPhone or iPad...😉 👍

-and some even wants a system with some quality speakers, instead of just a dockingstation...😐

And not everbody that does own an iphone and/or an ipad stores music on it and uses it as a music player...

😁

Ralf