I started posting in the other topic but I'll repeat here, this thread seems more specific to the topic.

The main backup improvement will be a pre-generated pool of keys and a rescan at load to scrape missed transactions from the block history.  Then a backup will last forward for a long time.

I was starting to post the same idea you said nelisky.

How about a json-rpc command that locks the wallet, flushes it, copies wallet.dat to a location you specified, then unlocks it?  That would be a smaller project than the pooled keys, so maybe it could be done first.

What's the simplest portable way to copy a file?  Is there something in Boost?

What should it be named?  maybe:
backupwallet <destination>